Innovations
• EMR 
Contribution à l’optimisation de l’architecture de parcs d’hydroliennes
Résumé : Pour faire face au réchauffement climatique, une transition énergétique de grande ampleur est impérative. Pour les pays disposant de vastes zones maritimes, comme la France, les Energies Marines Renouvelables (EMRs) peuvent constituer une part significative d’énergie à bas carbone. Les EMRs peuvent être produites à partir de la houle, du vent, des gradients de salinité… Dans cette thèse, nous nous focalisons sur l’énergie des courants de marée et leur exploitation par les hydroliennes. Cette technologie est aujourd’hui en phase pré-industrielle.Dans ce travail de thèse, un outil d’aide à la décision destiné à l’optimisation de l’architecture des parcs d’hydroliennes est développé. Cet outil nommé OPTIFARM tient compte de l’hydrodynamique du site, des coûts d’investissement et des opérations de maintenance, des pertes d’énergie de production dues aux effets de sillage ainsi que des pertes d’énergies dans le réseau électrique. L’outil permet de déterminer de manière optimale le nombre et les positions des hydroliennes et des sous-stations électriques offshores ainsi que la topologie de raccordement électrique en AC. OPTIFARM est basé sur un algorithme génétique et un algorithme d’optimisation par essaim particulaire. La méthode d'optimisation développée est appliquée à deux sites hydroliens français : le Raz-Blanchard (situé entre l'île d'Aurigny et le Cap de la Hague) et le passage du Fromveur (situé en mer d'Iroise) qui représentent respectivement le premier et le deuxième plus grand gisement hydrolien en France. Les résultats montrent que le coût de production de l'énergie diffère considérablement d'un site à l'autre et qu'il dépend fortement de la taille du parc.
Research on motion inhibition method using an innovative type of mooring system for spar floating offshore wind turbine
Résumé : Compared with the conventional floating offshore platforms, the FOWTs (floating offshore wind turbines) are subjected to larger wind heeling moments to cause significant pitch motions which bring challenges to the power generation efficiency and structure safety, due to the existence of wind turbines. In addition, the dynamic cable connected with FOWT is subject to a load that is greatly affected by horizontal motions of FOWT. Therefore, the inhibitions of horizontal and pitch motions are vital to FOWT. However, conventional mooring systems mainly inhibit the horizontal motions of floating structures. In this paper, an innovative type of mooring system is proposed to inhibit both the horizontal and pitch motions of FOWT. The analytical results based on the innovative mooring system are compared with those of conventional mooring system. In addition, the mechanism of restoring forces and moments of mooring systems are analyzed and discussed.
Connector for Connecting Together Underwater Cables and in Particular Umbilical Cables for Marine Renewable Energy Farms
Résumé : Le connecteur (10) comporte : - un boîtier de connexion (12) dans lequel les câbles pénètrent parallèlement l'un à l'autre et parallèlement à une première direction (X), et - un palonnier de manutention (16), relié au boîtier de connexion (12) par des moyens de liaison (18) articulés selon un axe (R) perpendiculaire à la première direction (X).
Estimating the Impact of Drone-based Inspection on the Levelised Cost of Electricity for Offshore Wind Farms
Résumé : Using drones for infrastructure inspection is becoming routine, driven by the benefit of reducing risk and costs. In this paper, the business case for drone-based inspection is examined from the perspective of the wind farm operator and the Drone Service Provider (DSP). A physical and financial model of an offshore wind farm is built using techno-economic analysis and activity-based costing, and data from the open literature. Drone operational models are developed based on domain specific knowledge of operation practices and the predicted physical environment. Rope-access inspection is used as a baseline and accounts for 0.7% of the wind farm operational expenditure. Replacing rope-access inspection with drones reduces costs by up to 70% and decreases revenue lost due to down-time by up to 90%. Increasing autonomy of drones increases the speed at which inspections can be performed but increases costs and complexity. For wind farm operator there is marginal economic benefit (2% reduction in inspection costs) in moving towards a fully autonomous drone-based inspection system from the current visual line of sight operation of single drone. However, from the point of view of the DSP, fully autonomous operations allow greater scalability of the business and enables higher utilisation of the fleet.
Mooring Damage Identification of Floating Wind Turbine Using a Non-Probabilistic Approach Under Different Environmental Conditions
Résumé : This paper discusses the damage identification in the mooring line system of a floating wind turbine (FWT) exposed to various environmental loads. The proposed method incorporates a non-probabilistic method into artificial neural networks (ANNs). The non-probabilistic method is used to overcome the problem of uncertainties. For this purpose, the interval analysis method is used to calculate the lower and upper bounds of ANNs input data. This data contains some of the natural frequencies utilized to train two different ANNs and predict the output data which is the interval bounds of mooring line stiffness. Additionally, in order to reduce computational time and more importantly, identify damage in various conditions, the proposed method is trained using constant loads (CL) case (deterministic loads, including constant wind speed and airy wave model) and is tested using random loads (RL) case (including Kaimal wind model and JONSWAP wave theory). The superiority of this method is assessed by applying the deterministic method for damage identification. The results demonstrate that the proposed non-probabilistic method identifies the location and severity of damage more accurately compared to a deterministic one. This superiority is getting more remarkable as the difference in uncertainty levels between training and testing data is increasing.
Investigation of long-term extreme mooring tensions by fully coupled dynamic analysis
Résumé : A numerical model which has been validated by the experimental data is used to simulate semisubmersible- taut mooring dynamic responses in a specified site of South China Sea. In order to take the random wave elevations into considerations, the short term analysis with different random wave seeds are carried to study the system dynamics. The mooring tension distributions in different significant wave heights and peak periods are fitted by the Weibull distributions. Different methods including the global maximum method, peakover-threshold method and short-term peaks method are applied to investigate the long term extreme mooring tension. The estimated long term extreme mooring tensions are compared, and the accuracy of these methods are discussed.
Analysis of tripod supported offshore wind turbines under conditions of marine growth
Résumé : Offshore wind turbines are now a mature technology to produce renewable energy on a vast scale, nonetheless several design and maintenance planning challenges remain. There have been attempts to investigate the impact of marine growth on fixed offshore wind turbine structures, but only few adopted a whole dynamics approach. This work presents a methodology to capture the influence of marine growth on the dynamic response of a tripod substructure, supporting the NREL 5 MW reference offshore wind turbine, under combined dynamic loads from wind and waves, and including soil-structure interaction by means of the spring-to-ground model. Marine growth is modelled as prescribed by DNV and API, evaluating the effects of variation of its thickness, roughness, and distribution. It is here demonstrated that marine growth thickness and roughness impact significantly on the loads acting on wind turbines' structures and its dynamic response, and that heterogeneity in marine growth thickness profiles vs depth available in literature lead to substantially different results. Tower top displacement becomes 24% higher when marine growth thickness grows from 0 to 200 mm. On the other hand, the changes in the natural frequencies of the support structure with an increase of marine growth's thickness are almost negligible (0.3%).
Biomimetic surface coatings for marine antifouling : Natural antifoulants, synthetic polymers and surface microtopography
Résumé : Marine biofouling is a ubiquitous problem that accompanies human marine activities and marine industries. It exerts detrimental impacts on the economy, environment, ecology, and safety. Traditionally, mainstream approaches utilize metal ions to prevent biological contamination, but this also leads to environmental pollution and damage to the ecosystem. Efficient and environmentally friendly coatings are urgently needed to prevent marine devices from biofouling. Since nature is always the best teacher for humans, it offers us delightful thoughts on the research and development of high-efficiency, broad-spectrum and eco-friendly antifouling coatings. In this work, we focus on the research frontier of marine antifouling coatings from a bionic perspective. Enlightened by three distinctive dimensions of bionics: chemical molecule bionic, physiological mechanism bionic, and physical structure bionic, the research status of three main bioinspired strategies, which are natural antifoulants, bioinspired polymeric antifouling coatings, and biomimetic surface microtopographies, respectively, are demonstrated. The antifouling mechanisms are further interpreted based on biomimetic comprehension. The main fabrication methods and antifouling performances of these coatings are presented along with their advantages and drawbacks. Finally, the challenges are summarized, and future research prospects are proposed. It is believed that biomimetic antifouling strategies will contribute to the development of nontoxic antifouling techniques with exceptional repellency and stability.
Reduction in Mooring System Lifetime due to Corrosion and Severe Storms
Résumé : We report on a multi-year investigation into mechanisms of fatigue, corrosion, and abrasion on floating offshore wind turbine (FOWT) mooring systems funded by the U.S. Bureau of Safety and Environmental Enforcement (BSEE). The project team examined the efficacy of standards-based design procedures as they relate to fatigue damage and material degradation.
Best practice design encourages applying 50% of a mooring chain corrosion allowance to fatigue calculation. However, the project team concludes that this practice may underestimate fatigue damage when the corrosion rate is high relative to the component diameter. A more robust accounting of corrosion rate in fatigue calculations decreased the predicted lifetime of a mooring system by over 80% in one small scale field deployed case study. This discrepancy was reduced in a similar comparison of a full-scale system.
Best practice design focuses on operational and normal sea states for fatigue damage calculation. The project team has concluded, through simulation of validated case studies, that severe storms may contribute significant fatigue damage to chain moorings. Over 50% of the fatigue on a prototype FOWT mooring was caused by storms which occur less than 0.2% of the time. A single 20-year storm produced over 15% of the anchor fatigue of a theoretical full-scale FOWT.
By augmenting standards-based predictions of the degradation rate of chain-based mooring systems through better accounting for corrosion and abrasion rates over the full lifetime of the mooring system and including rare, extreme storms in fatigue calculations, the engineer or developer can plan ahead and reduce the risk of dangerous and expensive failures.
Fatigue Analysis for Mooring System of a Spar-Type Floating Offshore Wind Turbine
Résumé : This paper aims to perform a time-domain mooring fatigue analysis for a Spar-type floating offshore wind turbine operated in the South China Sea. Tension ranges of mooring lines are achieved from a hydrodynamic analysis where the effects of wind, wave and current are considered. A rainflow counting method is used to calculate the number of mooring tension cycles with corresponding ranges. The fatigue lives of mooring lines are then predicted by Palmgren-Miner’s rule according to T-N & S-N curves. A comparison of fatigue lives predicted by T-N & S-N curves-based approaches with/without considering safety factors is made. The results show that the T-N curves-based approach is more conservative than the S-N curves-based approach if safety factors are not considered in the two approaches, while the fatigue lives predicted by both approaches are in general comparable when the safety factors suggested by API and DNVGL are applied in the two approaches. A comparative study of three kinds of R4 grade studless mooring chains with different diameters (2.5-inch, 4-inch, 5-inch) is also conducted and the results show that the design with the 2.5-inch chain does not meet the fatigue requirements.
Characteristic Analysis of High Temperature Superconducting Wind Turbine Generator
Résumé : Wind power as an important renewable energy form has been developed substantially. Nowadays, more and more offshore wind plants using large-scale direct-drive wind turbine generators (DD-WTG) have been developed. Among the high-power wind turbines, the large-scale high temperature superconducting (HTS) DD-WTGs are the potential candidate for the practical application. In this paper, the characteristics including advantages and disadvantages of HTS DD-WTG with different topologies have been analyzed and presented.
Offshore Wind, Wave and Integrated Energy Conversion Systems : A Review and Future
Résumé : The offshore wind and wave are two promising renewable resources to address the concerns about the repaid growing energy demand across the world and the reduction of dependency on fossil fuels. Although these two resources have experienced significant development in the past decades, few research studies have been identified discussing the electrical systems as a part of various power transfer topologies. There is a lack of study which effectively considers potential configurations of highly intermittent wind and wave energy source and their impacts on the entire system operation, system efficiency, reliability and grid connection. This paper aims to fulfil this gap and to provide a comprehensive review on the electrical systems that can be utilised in both wind and wave energy conversion systems. The types of generators and control systems with power electronics used in the offshore wind turbines are presented and compared. The operation principles within the wave energy converters are discussed and classified. The selection of generators in the wave power take-off systems are discussed. A comprehensive guideline for the development of future integrated systems is provided in this paper primarily to reduce the cost of offshore systems, increase energy yield and improve reliability, predictability and dispatchability.
Dynamic Analysis in Design and Operation of Large Floating Offshore Wind Turbine Drivetrains
Résumé : This thesis presents a versatile rotor-bearing simulation model, including elements required to model rolling-element bearings as main bearings in large floating offshore wind turbines. Furthermore, the thesis presents new knowledge on the dynamic behavior of a main bearing, based on field measurements in one of the world’s first floating offshore wind farms.
Larger wind turbines are a fundamental contribution to reducing cost of energy for installations on both floating substructures and bottom-fixed foundations. Increasing turbine size and rating requires lightweight and compact main bearing and drive train solutions and challenges established layouts, components selection and analysis methods used in the design process.
Floating wind turbines are necessary to access the full offshore wind power potential. Although pioneering floating wind farms exist and more are under planning, floating operation is currently not a design driver for the standardized rotor-nacelle assembly part of a turbine. It is simply a different set of conditions for which the calculated ultimate loads and the accumulated fatigue damage must not exceed the type certification basis.
Considering the solution spaces for drivetrains and floating substructures in combination with the limited experiences with larger turbines and floating operation, more knowledge on drivetrain load effects is needed.
Reliability problems in wind turbine gearboxes have partly been attributed to limited understanding of drivetrain dynamics. Numerous studies addressing design and analysis of gear-based wind turbine drivetrains have followed. Despite increasing interest in floating offshore wind turbines, only a few studies have assessed the effects of floating operation on the drivetrain. These studies generally point to the main bearings as the most critical components.
Main bearings have received limited attention in literature, regardless of the design challenges for large wind turbines. The main bearings are an integral part of the turbine’s load-carrying structure, and main bearing replacement commonly requires the removal of both the rotor and the nacelle. Consequently, the design life for the main bearings should match or exceed the design life of the turbine. This aspect is important with respect to life extension studies, as main bearings should not be regarded as readily replaceable. Development of cost-efficient solutions for heavy maintenance is critical for floating turbines, and the value of avoiding bearing replacement is potentially higher than for bottom-fixed turbines.
Modeling and simulation are essential for offshore wind power development. Global structural analyses and local drivetrain analyses are commonly performed separately, in what is termed the decoupled approach. The main bearings are effectively connecting these domains, and attention to the modeling requirements for main bearings is needed.
The model presented in this thesis is developed through consistent use of the bond graph method, providing a clear model structure. Body-fixed equations of motion are derived by using Lagrange’s method and contained in field elements. An alternative cage model and a flexible outer ring are introduced, providing a more complete modeling basis. Modal representation is used for the flexible bodies, including a solution for moving loads on the outer ring.
An example simulation of a generic rotor-bearing system during run-up with and without a bearing damage is included to demonstrate the capability and usefulness of the model for transient analyses. The simulation results illustrate that the behavior of the non-linear system during a transient is not intuitive or easily inferred from the characteristics of the individual parts.
The thesis also presents a first-tier experimental analysis based on field measurement data from a main bearing in a 6 MW turbine on a spar-type floating substructure. Circumferential strain in the stationary bearing ring has been measured in multiple positions by using Optical Fiber Bragg Grating sensor arrays.
Analyses of the data in the time domain and the frequency domain show that in-plane bending deflection occurs in the main bearing ring, largely driven by differential blade bending moments at 3P frequency caused by wind loads and with limited influence from floater motion. This is an important result for future design of floating offshore wind turbines. Furthermore, sum and difference frequencies in the measured response as the result of non-linear system behavior indicate that decoupled drivetrain analysis approaches, where global and local analysis are carried out separately, may be insufficient in some cases.
The results from the modeling and simulation contribute to advancing knowledge on rotordynamic system models suitable for studying rolling-element bearing dynamics in mechatronics- and control-related applications, during transient events and fault conditions, and subject to damage.
The results from the experimental analyses confirm the basis for the modeling requirements with respect to flexible ring representation and thus indirectly with respect to the importance of a cage. Furthermore, it can be inferred from the experimental analysis that the significance and implications of the results depend on the actual main bearing design and the turbine size. For some designs, it is recommended to consider performing coupled analysis and including the hub consistently as a flexible element in both drivetrain modeling and full-scale testing of the drivetrain, thus moving the load interface from the main shaft to the blade attachment.
A Critical Review on the Structural Health Monitoring Methods of the Composite Wind Turbine Blades
Résumé : With increasing turbine size, monitoring of blades becomes increasingly important, in order to prevent catastrophic damages and unnecessary maintenance, minimize the downtime and labor cost and improving the safety issues and reliability. The present work provides a review and classification of various structural health monitoring (SHM) methods as strain measurement utilizing optical fiber sensors and Fiber Bragg Gratings (FBG’s), active/passive acoustic emission method, vibration‒based method, thermal imaging method and ultrasonic methods, based on the recent investigations and promising novel techniques. Since accuracy, comprehensiveness and cost-effectiveness are the fundamental parameters in selecting the SHM method, a systematically summarized investigation encompassing methods capabilities/limitations and sensors types, is needed. Furthermore, the damages which are included in the present work are fiber breakage, matrix cracking, delamination, fiber debonding, crack opening at leading/trailing edge and ice accretion. Taking into account the types of the sensors relevant to different SHM methods, the advantages/capabilities and disadvantages/limitations of represented methods are nominated and analyzed.
Feasibility evaluation for non-contact ultrasonic inspection of mooring chains through marine growth
Résumé : Mooring chains are subject to dynamic loads and corrosion. A challenging aspect in assessing the integrity of mooring chains is the presence of marine growth. Marine growth removal is expensive, environmentally damaging, and includes the risk of restarting corrosion process. The focus of this research is on the feasibility of mooring chains assessment in the presence of marine growth using active and passive ultrasound techniques. The approach includes experimental and numerical investigations for fatigue and corrosion damage. In the experimental part, specimens with and without marine growth have been designed, manufactured, and subjected to a series of experiments to determine the transmission characteristics of ultrasound waves through marine growth and its interaction with damage. Fatigue crack signals were simulated on the specimens using Hus-Nelson source. For the investigated compositions, the signal amplitude drop due to the presence of marine growth. Accelerated corrosion experiments were conducted to reproduce corrosion-induced acoustic emissions. Corrosion-induced signals were successfully detected and localized. Active ultrasound experiments were conducted using guided waves. These waves were successfully excited and measured in the test sample with naturally-cultured marine growth. The investigation suggests that guided waves can have a high potential for identification of fatigue cracks in the mooring chains. These experiments were complemented with numerical simulation of the setup. For the sake of computational efficiency and accuracy, a higher-order spectral finite element method was used. Simulations were further extended to investigate and confirm the possibility of detection of surfacebreaking cracks in the test sample.
The effect of marine growth and damage severity on the modal parameters of offshore wind turbine supporting structures : an experimental study
Résumé : This contribution investigates the effect of marine growth and damage severity on the modal parameters of a scaled experimental model of a monopile used in supporting offshore wind turbines. A quick glimpse of the literature review reveals that this topic has not been well investigated as the majority of previous research focuses on the effect of marine growth on the hydrodynamic loads transferred to the test structure, with little focus on its effect on the modal parameters of a structure. Nevertheless, from a monitoring standpoint, it is important to differentiate between the effect of marine growth and damage on the modal parameters, especially when these parameters are used as damage indicators, further improving existing structural health monitoring techniques in determining if the changes observed in modal parameters are caused by actual damage rather than the growth of marine organisms with time. The results provided in this contribution provide differences between the effect of marine growth and damage, which is recommended to be included in current monitoring techniques. Furthermore, a recommendation to investigate the effect of damage on damping and, possibly, the potential of using changes in damping characteristics as damage indicators is also made.
Optimal configuration of a tidal current turbine farm in a shallow channel
Résumé : This study investigates the macroscopic features of tidal farm layouts optimized to maximize power production in an idealized shallow channel with steady unidirectional flow. By varying the number of turbines and optimization constraints, numerical experiments were conducted using OpenTidalFarm, an open-source solver for tidal farm optimization using PDE-constraint gradient-based optimization. To alleviate the computational complexity for identifying a global optimum, a concept of quasi-global optimum was introduced, a local optimum that serves as a global optimum in a crude sense. From extensive numerical results, notable patterns in the shape of the quasi-global optimal layout were observed and explained by a nondimensional parameter, E, the ratio of the shortest hypothetical linear fence to the length of the lateral farm site constraint. The quasi-global optimal layout had a linear fence shape when E ≤ 1. The layout evolved into a downstream-concave parabola and subsequently into a V-shape as E increased beyond 1. Moreover, as more turbines were added to an array, the quasi-global optimal layout was no longer a single fence, and some turbines were separated from the main body. From the quantitative perspective, it is shown that the power production could be increased by up to 50% by tuning the optimization constraints.
Floating wind power platform
Résumé : A floating wind power platform for offshore power produc
tion includes a floating unit , wherein the floating unit
includes a first , a second and a third interconnected semi
submersible column each having a longitudinal column
central axis and each being arranged in a respective corner
of the floating unit , a first and second wind turbine , arranged
to the first and second semisubmersible columns , respec
tively , via a first and second tower respectively , wherein the
first and second towers have a first and second longitudinal
tower central axis , respectively , wherein the first and second
semisubmersible columns are arranged in the floating unit
with a first and second angle ( aj , A2 ) respectively , with
respect to a reference direction ( z ) , and directed away from
each other , wherein the first and second longitudinal tower
central axes are parallel to the first and second longitudinal
column central axes , respectively
Vibration of Flexible Member in Offshore Structures
Résumé : There are many flexible vertical members in offshore platforms like mooring lines and risers. These are exposed to wave, vessel motion and drilling loads during operation. For the smooth operation of these structures, the lateral excursion of these members should be minimal. This paper explains about the vibration analysis of a flexible vertical member subjected to base excitation. Initially, the flexible member was analysed as a SDOF non-linear spring-mass system. A qualitative understanding of the system was determined by solving the system using continuation method. Further, a numerical and experimental analysis was carried out on this member. Numerically, the member was analysed as an Euler–Bernoulli beam in MATLAB using the finite element method with three degrees of freedom at each node. The buckling load was determined using the Eigen value analysis. The minimum length required for buckling under gravity load was determined. The system was subjected to base excitation and the variation in the maximum response with respect to base excitation frequency was noted in the axial and lateral direction. The maximum response was obtained near the resonant frequency. Experimentally, the flexible member with a force transducer at its base was connected to the modal exciter through a stinger. The material of the member chosen was acrylic polymer as it buckles easily and can be used for testing. Forced excitation was provided using the modal exciter. On varying the frequency, the response of the member was observed. The length of the member was also a parameter that was varied such that the excursion was within controllable limits. Also, the area of the cross section in the upper half of the section was increased as an additional parameter for controlling the excursion. It was observed that the excursion was reduced as obtained from the theoretical analysis.
Design and comparative analysis of alternative mooring systems for floating wind turbines in shallow water with emphasis on ultimate limit state design
Résumé : Floating wind turbines represent a cost-efficient energy solution in deep water where bottom-fixed wind turbine becomes excessively expensive. However, mooring design is quite challenging for all shallow water depths including the transition water depth between bottom-fixed and floating wind turbines, in the order of 50–80 m, for which floating concepts might become more cost-effective than bottom-fixed ones. In this paper, mooring system design for floating wind turbine in shallow water are studied considering both catenary and taut mooring systems. Seven mooring concepts designed for a 5 MW semi-submersible floating wind turbine at 50 m water depth are compared with the purpose to identify solutions that are structurally reliable and economically attractive. The concepts are made of different mooring line materials (chain and synthetic fibre rope), mooring components (clump weight and buoy) and anchors (drag embedment anchor and suction anchor). Based on the latest experimental data, the nonlinear tension-dependent stiffness of synthetic fibre rope are described with an improved numerical model. Performance of the seven mooring concepts are compared with respect to mooring line characteristics, motion response amplitude operator, utilization factor considering the ultimate limit state design and cost etc. Six mooring design concepts are finally recommended for future assessment regarding the application of floating wind turbines in shallow water say 50 m and deeper.
Simplified design of new hybrid monopile foundations for offshore wind turbines
Résumé : First, a review of knowledge developed over the previous 50 years was presented, including various simplified methods of analyzing hybrid foundations. To discuss this subject comprehensively, a reference to calculations of piles was also made. On this basis, the author focused in the paper on new aspects of designing the hybrid foundations in serviceability limit states. The know-how review showed that the aspects of hybrid foundation design have been poorly recognized so far. For practical reasons, a simple calculation method for the hybrid foundations, useful for initial decision making, is still needed. A new design method was presented, based on a hybrid pile-soil interaction concept. A general design concept was described, the assumptions were formulated, and the method was explained in detail. A practical application of this method has been demonstrated for a large diameter hybrid pile, previously tested at full scale under lateral load. The calculation results were compared with the well-verified data obtained from the field test. By incorporating the extended knowledge on the mechanism of the pile-soil interaction, a significantly reduced horizontal stress in front of the pile was achieved. The conducted calculations confirmed that the hybrid monopile displacement is 40–70% lower compared to the standard monopile with similar dimensions. This method allows the stability of the new hybrid monopiles under lateral load to be assessed in a better way. The gained experiences can be useful for designers and other researchers to enhance the design of offshore wind turbines on monopiles.
Overall tidal farm optimal design–Application to the Alderney Race and the Fromveur Strait (France)
Résumé : This article presents an overall optimization method of Tidal Energy Converters arrangement and their electrical connection topology. This methodology is implemented as a software tool and formulated as a bi-level programming where two sequential genetic algorithms are used. A semi-analytical method is adopted to evaluate the loss of production caused by the wake effect. Electrical connection costs as well as line losses are taken into account. This developed tool takes a large panel of variables into consideration and delivers an optimal number of turbines and their locations, optimal AC electrical architecture and optimal sizing of electrical equipment as its output. The optimization approach is applied to the Alderney Race and the Fromveur Strait which represent the first and the second greatest tidal potential in France, respectively. The results show that the energy production cost considerably differs from one site to another and it strongly depends on the size of the farm.
Hydrodynamic Performance of Spar-Type Wind Turbine Platform Combined with Wave Energy Converter
Résumé : In the present study, the numerical investigation of 5 MW spar-type floating offshore wind turbine (FOWT) combined with array of four and six cone–cylindrical shaped heaving type point absorber is performed. Hydrodynamic and multibody analysis is carried out for simple spar, spar combined with circular array of four and six wave energy converters. Individual responses for all wave energy converters are obtained and their effect on spar platform is analyzed. The performance of combined wind and wave energy device is studied on analyzing the motion of platform. The influence of array of wave energy converters on hydrodynamic motion responses on spar platform is analyzed. The Response Amplitude Operator (RAO) for all the three platforms is compared and analyzed for the hydrodynamic stability of platform. The present study will be helpful in the design of novel concept of spar combined with circular array of wave energy converters.
Numerical and analytical analysis of a monopile-supported offshore wind turbine under ship impacts
Résumé : Offshore wind turbines in the vicinity of ship traffic are exposed to increased risks of ship collisions. To better understand the impact mechanism, this paper evaluates the dynamic responses of a monopile-supported wind turbine under ship impacts, using both numerical and analytical methods. The nonlinear finite element method is applied during the numerical simulations, and the wind load effects, soil conditions, and rigid and deformable ship bows are considered. The analytical approach, originally developed based on the energy method, is extended here to address the damping effects of monopile-supported wind turbines. In the case study, the impacts are studied between a 4600-ton vessel and a 5-megawatt offshore wind turbine. The effects are presented of the aerodynamic damping, ship impact velocity, mean wind speed, wind direction, and ship bow stiffness on the collision responses. A comparison between the numerical and analytical results shows a generally good agreement for the maximum contact force. Under an impact velocity of 1 m/s and 3 m/s, the discrepancy between the two methods is 5% and 7%, respectively. The developed engineering approaches can be used to address accidental collision problems between ships and bottom-fixed offshore wind turbines.
Dynamic failure analysis of renewable energy systems in the remote offshore environments
Résumé : For effective integrity management of marine renewable energy systems in the dynamic and uncertain ocean environments, understanding the failure dynamics is crucial. The cost of investment in marine/offshore renewable energy infrastructures and the associated cost due to failure and loss of energy production necessitate a predictive monitoring methodology that is dynamic and adaptive. This paper presents an integrated multi-state pure-birth-pure-death Markovian-net profit value model for the offshore turbine subsystem failure analysis and its cost-based consequences. The integrated model captures the offshore turbine subsystem's dynamic failure states and its economic implications due to the cost of energy loss and downtime for the period under consideration. The model applies a phase-type exponential distribution to describe the monotonic state of failure. The methodology is demonstrated with an offshore wind turbine gearbox, and it captures the dynamic state of the system and its failure mechanisms. The cumulative effect of the subelements deterioration decreases the gearbox performance by over 35% within the first 2 years of operation.
Energy absorption characteristics in hybrid composite materials for marine applications under impact loading : Case of tidal current turbine
Résumé : The tidal current turbine is the most efficient way to extract energy from the sea. This system can be prone to critical loads such as impact accidental in the installation and maintenance phase. Indeed, several complex modes of damage susceptible to harming the stability of the structure are studied to conceive hybrid composite nozzles with better resistance to damage. For this reason, two scenarios of low-velocity impact of a hybrid composite nozzle (glass/carbon) were investigated. In both cases, the impact was realized in the region of the trailing edge of the nozzle, and the results obtained were compared between three different laminated. On the other hand, damage modeling was formulated using the finite element method based on the Hashin criteria. Energy conservation of the nozzle was verified to validate the numerical model. Also, the effects of the impact velocity and the panel's flexibility on the initiation and propagation of damage have been studied. Depending on the results, the stacking sequence significantly influences the formation of damage. However, the results show that the hybrid nozzle with CGG (carbon/glass/glass) stacking has a higher impact resistance compared to other laminates.
LAHMANN, BENJAMIN. 2020. Impact of Digital Supported Process Workflow Optimization for Knee Joint Endoprosthesis Implantation on Hospital-Specific Process and Quality Ratios, pp. 105–107. In : David Hampel, Hana Vránová (eds.). PEFnet 2020. European Scientific Conference of Doctoral Students. Mendel University in Brno.
Résumé : Retrospective case-control study with a raw dataset of 297 cases. Estimating propensity scores with a logit model to balance the covariates in both groups to reduce confounders. Statistical analysis of efficiency and quality ratios of knee joint endoprosthesis implantations.
An Attachment Recognition Method Based on Image Generation and Semantic Segmentation for Marine Current Turbines
Résumé : Marine current turbine (MCT) is an efficient device for the utilization of marine current energy. As MCTs operate underwater for a long time, marine growth will attach to the machinery. Therefore, it is essential to recognize attachment on MCTs, since an increase in attachment will potentially deteriorate the power generation quality. Semantic segmentation is a suitable technique to perform this task, which however requires a large amount of labeled data. To acquire sufficient data, a specialized image generation method without high manual cost is proposed. For precise attachment recognition on blurry underwater images, we propose an improved semantic segmentation network (C-SegNet); this network adopts multi-scale feature concatenation and transfer learning to enhance the quality of recognition results. Besides, we use weighted cross-entropy loss to make the network pay more attention to some difficult segmentation objects. In the inference phase, dropout is utilized to estimate the recognition uncertainty, and a precise attachment area ratio is computed. Experimental results confirm the effectiveness of the proposed method under a submerged scene. In addition, C-SegNet has better performance than other state-of-the-art segmentation networks.
Towards Efficient High-fidelity Simulations of Wind Farms
Résumé : Aerodynamic simulations of wind farms are essential for the assessment of the power production
and loads of wind turbines. To date, such computations rely on low-fidelity engineering
models in the industrial practice, implying large uncertainties. On the other hand, the application
of high-fidelity computational fluid dynamics (CFD) remains limited to academic casestudies
due to the large computational demand. The lattice Boltzmann method (LBM) has developed
into a promising alternative to classical CFD models. Particularly, GPU-based (graphics
processing unit) implementations of the method provide significant performance gains alleviating
the computational constraints of other approaches. This thesis investigates the potential of
the LBM for wind turbine simulations. On this account, an aerodynamic wind turbine model
using the actuator line technique is coupled to a lattice Boltzmann framework. This novel implementation
is analysed in terms of the aerodynamic forces acting on the wind turbine blades,
as well as the properties of the wake of the turbine. First of all, it is shown than the utilised
cumulant lattice Boltzmann scheme is sufficiently robust for the investigated flow cases. Furthermore,
the studies show that the presented set-up compares well to well-established CFD
models in the field. At the same time, the reduction in computational demand is found to be
large enough to allow for overnight-runs of typical industrial simulation cases.
Transient Response of a Spar-Type Floating Offshore Wind Turbine with Fractured Mooring Lines under Stochastic and Freak Wave Scenarios
Résumé : The Spar-type FOWT, which is a kind of the stable offshore wind generator, has been widely adopted and investigated in recent years. As a permanent mooring structure, it faces the issue on mooring line fracture. In the present work, the simulations are conducted in time domain to investigate its transient response in scenarios with fractured mooring lines. Towards this end, our in-house code SFND, which is a coupled aero-hydro-elastic numerical model is adopted to perform the simulations. The methodology includes a blade-element-momentum model for aerodynamics, a nonlinear model for hydrodynamics, a nonlinear restoring model of SPAR buoy, and a fully nonlinear dynamic algorithm for intact and fractured mooring lines. The simulations are conducted under both stochastic and freak wave scenarios. The motions of platform, the tensions in the mooring lines and the power generation performance are documented in different cases. According to the results, the large drift motion is observed and the transient response is discussed.
Cumulative effects of marine renewable energy and climate change on ecosystem properties : Sensitivity of ecological network analysis
Résumé : In an increasingly anthropogenic world, the scientific community and managers have to take interactions between the drivers of ecosystems into consideration. Tools like ecological network analysis (ENA) indices offer the opportunity to study those interactions at the ecosystem level. However, ENA indices have never been used to test the incidence of cumulative drivers. The present study uses models combining the effects of (i) the reef caused by the future offshore wind farm of Courseulles-sur-Mer and (ii) climate change on species distribution, to test the response of multiple ENA indices. ENA indices proved sensitive to this cumulative impact, displaying a wide variety of cumulative effects. They were also very powerful to characterize the role of the cumulative impact on ecosystem functioning. These results demonstrate the capacity of ENA indices to describe and understand cumulative effects at the ecosystem scale. Using a sensitivity analysis approach, this study shows that ENA indices could be viable tools for managers. To help them in their tasks, the next step could be to link ecosystem services to ENA indices for a more practical use.
Floating Wind Turbines and Wind Energy Cost Analysis
Résumé : Largely motivated by concern about emission of greenhouse gasses, engineers and scientists have increasingly turned towards renewable and clean energies. Wind power is currently the leader in renewable energy supply across the globe. However harnessing energy from wind is not a recent invention. Wind has been used to drive mechanical processes such as milling grain since around 600BC in the age of the Persian empire and perhaps even earlier in ancient Egyptian civilizations as well (Jamieson & Hassan, 2011; Hau, 2013). Although wind power has never been used quite as extensively as it is currently at 7.3% of the entire U.S. energy supply (EIA - Independent Statistics and Analysis, 2020). First the fundamental principles guiding wind turbine design will be introduced in Section 2. Then Section 3 will dive deeper into research and progress in increasing wind turbine e_ciency and creating wind farms at scale. Sections 4 and 5 will introduce o_shore wind turbines and oating wind turbines as well as the particular bene_ts but also challenges of o_shore wind farms. Finally Section 6 will briey go over the current and projected costs of onshore and o_shore wind energy. The e_ciency and cost analyses will ultimately lead to the conclusion that o_shore wind farms are likely to remain useful sources of renewable energy in regions where space and noise and visual pollution are concerns, while meanwhile in regions without limited land supply, onshore wind farms are one of the most cheap and e_cient sources of energy period.
Design load estimation with IFORM-based models considering long-term extreme response for mooring systems
Résumé : In this paper, we present an extension of the alternative environmental contour approach based on inverse first-order reliability theory in a three-dimensional model that accounts for short-term extreme response uncertainties. Subsequently, the long-term extreme tension under wave excitation loads is investigated to evaluate return levels for the design of mooring systems. Tension extreme data are derived from time-domain simulations of a floating coupled system using the peak-over-threshold method to determine short-term load distribution. A linear interpolation scheme is utilised to establish the parametric model using distribution parameters and wave data. Long-term extreme loads are estimated using a simplified discrete approach combined with Monte Carlo simulations, which helps avoid the tedious task of direct integration. The applicability of these load assessment models is demonstrated and discussed using an example of a semi-submersible platform situated at a 500-m water depth, and the results are compared with one- and two-dimensional environmental contour-based models.
Crack growth direction effects on corrosion-fatigue behaviour of offshore wind turbine steel weldments
Résumé : In this study corrosion-fatigue tests have been conducted on fracture mechanics specimens extracted from an S355 G10+M structural steel welded plate. The tests have been performed on compact tension specimens with the crack tip located in the heat affected zone. The corrosion-fatigue test results from this study have been compared with the data available on the base metal as well as air tests on the same material. Moreover, the obtained results have been compared with the corrosion-fatigue data available in the literature on a wide range of steels and also the fatigue trends for welded joints in free-corrosion condition recommended in the BS7910 Standard. The effect of the specimen orientation, with respect to the weld region, is also examined in this study and it has been found that higher corrosion-fatigue crack growth rates are generally observed in the tests with 0° orientation. The results have also shown that the corrosive environment has significant effects on the fatigue crack growth acceleration at the beginning of the tests; however, as the crack propagates, the environmental damage effect on crack growth behaviour becomes less pronounced. The results presented in this study are discussed in terms of improvement in the structural integrity assessment of offshore wind turbine monopiles.
Analysis of the influence of climate change on the fatigue lifetime of offshore wind turbines using imprecise probabilities
Résumé : When discussing the connection of wind energy and climate change, normally, the potential of wind energy to reduce green house gas emissions is emphasised. Hence, effects of wind energy on climate change are analysed. However, what about the other direction? What is the impact of climate change on wind energy? Recently, the effect of a reversal in global terrestrial stilling,that is, an increase in global wind speeds in the last decade, on the wind energy production has been analysed. Certainly, knowledge about potential changes in energy production is essential to plan future energy supply. Nonetheless, at least similarly important is the effect on loads acting on wind turbines. Increasing loads due to higher wind speeds might reduce wind turbine lifetimes and yield higher costs. Moreover, especially for already existing turbines, it might even affect the structural reliability. Since the impact of climate change on wind turbine loads is largely unknown, it is studied in this work in more detail. For this purpose, different existing models for predicted changes in wind speed and air temperature and their uncertainties are used to forecast the environmental conditions an exemplary offshore wind turbine is exposed to. Subsequently, for this turbine, the lifetime fatigue damages are calculated for different prediction models. It is shown that the expected changes in lifetime fatigue damages are present but relatively small compared to other uncertainties in the fatigue damage calculation.
Analytical Assessment of the Mooring System Stiffness
Résumé : The definition of the mooring systems is one of the most important stages on the design any
offshore unit. Some effects associated with it, on the responses of the floating body, are still
under investigation. In this context, the full nonlinear high-order hierarchical modeling and
the numerical integration of the resulting equations of motion might not be the most cost
effective approach for the evaluation of those effects during the early design process. Thus,
an expedite analytical formulation to assess the mooring system stiffness, a tool that could
help the initial design and analysis. Using classic approaches from Analytical Mechanics,
the nonlinear generalized restoring forces associated with the mooring acting on the vessel
due to the mooring lines are formulated. The six-degree-of-freedom (DoF) problem is
herein addressed. The stiffness matrix is obtained from the linearization of the generalized
forces around a generic position. Mooring line characteristic tension function is an input of
the method. The closed formulation does not requires a specific line model, although the
formulation for a multi-segment mooring line is also derived. The methodology is applied
taking the OC4-DeepCwind Floating Wind Turbine semi-submersible platform as a case
study. Two Spread Mooring Systems arrangements are studied, in order to demonstrate
the use of the presented formulation as a design tool. The calculated mooring system
stiffness matrix, evaluated at the trivial equilibrium position, exhibits good agreement
with numerical results found in the literature by high hierarchy models. Additionally, the
stiffness coefficients are evaluated for other positions than the trivial equilibrium one in the
form of colored maps. The natural periods of the motions on the horizontal plane are also
mapped. These maps help to understand the effects of the static vessel mean position on
the mooring system stiffness and, consequently, on the natural periods associated with the
motions on the horizontal plane. Considering the original OC4 mooring system, the effects
of the mooring line pre-tensioning are also investigated. Some conclusions on the axial
stiffness of catenary cables are also made. The main contributions of the present master
dissertation are: (i) the stiffness matrix analytical closed formulation and (ii) the use of
colored maps to evaluate the stiffness and the natural periods as functions of the mean
offset position. The present master dissertation brings then an innovative closed-form
formulation with important practical applications.
Rotational sampling of waves by tidal turbine blades
Résumé : The presence of waves exposes tidal stream turbines to large and cyclic hydrodynamic loads which significantly influence the design requirements for tidal turbine blades. Here we describe a loading phenomenon not previously considered in literature caused as blades rotationally sample an oscillating and vertically decaying wave-induced velocity field. Although implicitly incorporated into numerical models, the dominant causes and relative influence have not previously been considered.In this article this effect is described through theoretical analysis and validated through scaled experiments; including irregular waves at angles to the rotor and current field. The associated loads are found to be strongly correlated to the wavenumber. The nature of the rotational-sampling-effect is confirmed through analysis of the experimental results, where characteristic sidebands are effectively predicted in the blade root bending moment spectra. It is estimated to account for between 8% and 16% of the fatigue damage and between 7% and 13% of the peak root bending moment for the conditions tested. A key finding is that two bilaterally-symmetrical oblique wave conditions do not produce equivalent loading patterns: one produces higher frequency oscillations. Additionally, it is found that the frequency of these loads reduces linearly with rotational speed; highlighting another consideration for tidal stream turbine operation.
A low-order wake interaction model for ocean current turbine arrays operating in turbulent flow
Résumé : Ocean Current Turbines (OCTs), which function similarly to wind and tidal turbines, represent a promising technology for harnessing the energy from oceanic currents. The power extracted by the turbines can be significantly affected by the turbulence intensity in the upstream flow. For turbines distributed in an arrayed configuration, the highly turbulent wakes behind each upstream turbine must also be considered. In this presentation, we describe a low-order analytical wake interaction model capable of estimating the total array power of OCTs operating in any stacked configuration, and embedded in a flow with Turbulence Intensity (TI). The model incorporates both near and far-wake effects associated with each turbine, and has been validated using high-resolution Large Eddy Simulations (LES) performed using the STAR-CCM software. The simulations were driven by realistic ocean turbulence conditions derived from Gulf Stream current measurements. The analytic model was validated over a wide range of turbulence intensities and OCT array configurations, and can also be applied to evaluate the performance of wind turbine installations.
Numerical simulation of violent breaking wave impacts on a moored offshore wind turbine foundation over nonuniform topography
Résumé : Breaking wave impact on a moored offshore wind turbine foundation over a variable-depth seabed is considered in time domain, based on the fully nonlinear potential theory. An adiabatic model is used to simulate the variation in air cavity volume and pressure imposed on the dynamic boundary condition of the inner free surface. The whole impact process is solved using the dual coordinate system, where a local stretched coordinate system is adopted to determine both the shape and location of the initial impact zone, while the global coordinate system is applied to track further development of both the upper and lower jets. A higher-order boundary element method is introduced to establish water integral equations of the main fluid domain and the thin jet, which are combined together with the match conditions of pressure and velocity on the interface. By employing auxiliary functions, the temporal derivative of velocity potential is accurately obtained to decouple the mutual dependence of body and fluid motions. A specified global coordinate-based finite element method is used to derive the dynamic equilibrium equation of the mooring line element. Through the hinged condition at the fairlead location, the motion equations of the wind turbine and its mooring system are simultaneously solved using the Newton–Raphson iterative method. Extensive simulations are performed and discussed for the free surface profile, pressure distribution, body motion, and air cavity features. The wind turbine moored at the seabed with larger slope was found to experience relatively higher air cavity pressure and achieve larger rotational speed, smaller horizontal, and vertical speed.
Plus de références EMR
• Biocorrosion
Characterization of microbiological influence corrosion for API 5L X46 pipeline by sulphate-reducing bacteria (SRB)
Résumé : In this study, the microbiological corrosion behavior of API 5L X46 low steel taken from damaged petroleum transporting pipeline used in Babylon-Iraq were investigated. A swab of samples taken from the area of damage was analyzed by polymer chain reaction device to find out the type of corrosive bacteria present, Desulfovibrio sp was found, which is a sulfide reducing bacteria, and this was confirmed by the analysis of corrosive products X-ray diffraction. Two attacking media were used, the first medium (A) representing the surrounding dead water in the pipeline and the second (B) is a “medium bar” in which sulfur-reducing bacteria were cultivated, the specimens were placed in it for 28 days. Simple immersion test was don; the result show that the A medium has higher percentage of weight loss than B medium. Pure elements, compounds and ions were analyzed for the surrounding water. Scan electron microscope and Energy Dispersive Spectroscopy examination of the surface of the specimens was conducted, which gave pictures of the existing bacteria, as the medium (A) only the sulfide bacteria appeared in specimens grown, while the B medium has a completely different surface nature from other media, and this is due to the absence of the role of bacteria in it. X-ray diffraction test showed corrosion products taken from samples of all mediums, different results were shown, the compounds present in the medium (A) was associated with the products containing sulfur in their composition only is (FeS), and the medium (B) showed different compounds from the previous two mediums, the most prominent of which were the compounds (FeNO3), which is a compound that may have its source from the interaction of the surrounding environment with the mineral or through the fact that the area is agricultural and it is used in pest control.
Comparison of 304 and 316 stainless steel microbiologically influenced corrosion by an anaerobic oilfield biofilm consortium
Résumé : Stainless steel (SS) has wide applications in oilfields because of their outstanding corrosion resistance. However, SS is susceptible to localized MIC (microbiologically influenced corrosion). In this study, the MIC caused by an oilfield mixed-culture consortium (labelled as Consortium II) in enriched artificial seawater against commonly utilized 304 SS and 316 SS was evaluated. Sessile cell count results showed that Consortium II had better growth on 304 SS surface than on 316 SS with 79% more sulfate reducing bacteria (SRB) and 37% more acid producing bacteria (APB). Pitting corrosion was observed. The corrosion resistance (Rp) from linear polarization resistance (LPR) of 316 SS was two times as much as that for 304 SS during the 14-day incubation, while the corrosion current density (icorr) of 304 SS was 101 higher than that for 316 SS (2.19 µA/cm2 vs. 0.19 µA/cm2) at the end of the incubation. These results suggested that 316 SS was considerably more resistant to MIC by the oilfield biofilm than 304 SS.
Multifunctional Inhibitor Mixture for Reducing Bacteria Growth and Corrosion on Marine Grade Steel
Résumé : Europe PMC is an archive of life sciences journal literature., Multifunctional Inhibitor Mixture for Reducing Bacteria Growth and Corrosion on Marine Grade Steel
Microbiologically Influenced Corrosion Behavior of Carbon Steel in the Presence of Marine Bacteria Pseudomonas sp. and Vibrio sp.
Résumé : The microbiologically influenced corrosion (MIC) behavior of carbon steel is investigated in the presence of Vibrio and Pseudomonas. Sterilized natural seawater inoculated with Pseudomonas, Vibrio, and the mixture of Pseudomonas and Vibrio, separately, and they are utilized as the media for corrosion characterizations, which are closer to the natural environment in seawater. Weight loss measurements, electrochemical techniques (the open-circuit potential, electrochemical impedance spectroscopy (EIS), and potentiodynamic polarization curves), and surface analysis (scanning electron microscopy (SEM)) are performed to explore the synergistic effect of Pseudomonas and Vibrio on the corrosion behavior of carbon steel. As seen from the growth curves of bacteria, the growth and propagation of Pseudomonas and Vibrio are affected by their metabolic activities. Besides, the results obtained by SEM show that more severe pitting corrosion is observed on the coupons exposed to the sterilized natural seawater inoculated with the mixture of Pseudomonas and Vibrio. Further, the results from electrochemical measurements and weight loss measurements suggest that under the synergistic effect of Pseudomonas and Vibrio, the initial corrosion rate of carbon steel is inhibited, while the latter corrosion is enhanced.
The oil spill and the use of chemical surfactant reduce microbial corrosion on API 5L steel buried in saline soil
Résumé : In order to evaluate the biocorrosion of API 5L metal buried in saline soils, three different conditions in microcosms were evaluated. The control microcosm contained only saline soil, the second had the addition of petroleum, and the third contained the addition of both petroleum and surfactant. The corrosion rate of the metals was measured by loss of mass after 30 days, and the microbial communities were delineated using 16S rRNA gene sequencing techniques. The species were dominated by halophiles in all samples analyzed. Among the bacteria, the predominant group was Proteobacteria, with emphasis on the Alphaproteobacteria and Gammaproteobacteria. Betaproteobacteria and Deltaproteobacteria members were also identified in a smaller number in all conditions. Firmicutes were especially abundant in the control system, although it was persistently present in other conditions evaluated. Bacteroidetes and Actinobacteria were also present in a considerable number of OTUs in the three microcosms. Halobacteria were predominant among archaea and were present in all conditions. The analysis pointed to a conclusion that in the control microcosm, the corrosion rate was higher, while the microcosm containing only oil had the lowest corrosion rate. These results suggest that, under these conditions, the entry of other carbon sources favors the presence of petroleum degraders, rather than samples involved in the corrosion of metals.
Influence of NaCl concentration on microbiologically influenced corrosion of carbon steel by halophilic archaeon Natronorubrum tibetense
Résumé : The influence of NaCl concentration on microbiologically influenced corrosion (MIC) of Q235 carbon steel by the halophilic archaeon Natronorubrum tibetense was investigated by immersion tests and electrochemical measurements. An increase in NaCl concentration from 0 g/mL to 0.1 g/mL promoted the anodic dissolution of carbon steel and accelerated its corrosion, but MIC did not occur. A further increase in NaCl concentration to 0.2 g/mL led to MIC in inoculated medium, and the occurrence of the MIC resulted in further aggravation of carbon steel corrosion. Once the NaCl concentration reached 0.3 g/mL, the high concentration of chloride ions greatly interfered with the adsorption of dissolved oxygen and the attachment of N. tibetense cells to the surface of carbon steel, thus reducing the corrosion rate of carbon steel and inhibiting the MIC.
Characterization of microbiologically influenced corrosion by comprehensive metagenomic analysis of an inland oil field
Résumé : Corrosion in pipelines and reservoir tanks in oil plants is a serious problem in the global energy industry because it causes substantial economic losses associated with frequent part replacement and can lead to potential damage to entire crude oil fields. Previous studies revealed that corrosion is mainly caused by microbial activities in a process currently termed microbiologically influenced corrosion or biocorrosion. Identifying the bacteria responsible for biocorrosion is crucial for its suppression. In this study, we analyzed the microbial communities present at corrosion sites in oil plant pipelines using comparative metagenomic analysis along with bioinformatics and statistics. We analyzed the microbial communities in pipelines in an oil field in which groundwater is used as injection water. We collected samples from four different facilities in the oil field. Metagenomic analysis revealed that the microbial community structures greatly differed even among samples from the same facility. Treatments such as biocide administration and demineralization at each location in the pipeline may have independently affected the microbial community structure. The results indicated that microbial inspection throughout the pipeline network is essential to prevent biocorrosion at industrial plants. By identifying the bacterial species responsible for biocorrosion, this study provides bacterial indicators to detect and classify biocorrosion. Furthermore, these species may serve as biomarkers to detect biocorrosion at an early stage. Then, appropriate management such as treatment with suitable biocides can be performed immediately and appropriately. Thus, our study will serve as a platform for obtaining microbial information related to biocorrosion to enable the development of a practical approach to prevent its occurrence.
Anticorrosive Properties of Green Silver Nanoparticles to Prevent Microbiologically Influenced Corrosion on Copper in the Marine Environment
Résumé : Microbiologically influenced corrosion is a global problem especially materials used in marine engineering. In that respect, inhibitors are widely used to control fouling and corrosion in marine systems. Most techniques used in inhibitor production are expensive and considered hazardous to the ecosystem. Therefore, scientists are motivated to explore natsural and green products as potent corrosion inhibitors especially in nano size. In this study, antibacterial and anticorrosive properties of green silver nanoparticles (AgNPs) were studied through weight loss, electrochemical characterization, and surface analysis techniques. The corrosion of copper (Cu) in artificial seawater (ASW), Halomonas variabilis (H. variabilis) NOSK, and H. variabilis + AgNPs was monitored using electrochemical measurements like open circuit potential (OCP), electrochemical impedance spectroscopy (EIS), and potentiodynamic polarization curves. AgNPs showed excellent antibacterial activity against pathogenic microorganisms. Electrochemical studies demonstrate a noticeable decrease in OCP and current density in ASW containing H. variabilis + AgNPs compared to both ASW and ASW inoculated with bacterium, which confirmed the decrease of corrosion rate of copper. Furthermore, the obtained voltammograms show that the silver nanoparticles were adsorbed on the copper electrode surface from the corrosion solution. Thus, the results prove that the novel idea of green silver nanoparticles acts as an anticorrosive film in the marine environment.
Responses of soil microbiome to steel corrosion
Résumé : The process of microbiologically influenced corrosion (MIC) in soils has received widespread attention. Herein, long-term outdoor soil burial experiments were conducted to elucidate the community composition and functional interaction of soil microorganisms associated with metal corrosion. The results indicated that iron-oxidizing (e.g., Gallionella), nitrifying (e.g., Nitrospira), and denitrifying (e.g., Hydrogenophaga) microorganisms were significantly enriched in response to metal corrosion and were positively correlated with the metal mass loss. Corrosion process may promote the preferential growth of the abundant microbes. The functional annotation revealed that the metabolic processes of nitrogen cycling and electron transfer pathways were strengthened, and also that the corrosion of metals in soil was closely associated with the biogeochemical cycling of iron and nitrogen elements and extracellular electron transfer. Niche disturbance of microbial communities induced by the buried metals facilitated the synergetic effect of the major MIC participants. The co-occurrence network analysis suggested possible niche correlations among corrosion related bioindicators.
Microbiologically Influenced Corrosion Behavior of Carbon Steel in the Presence of Marine Bacteria Pseudomonas sp. and Vibrio sp.
Résumé : The microbiologically influenced corrosion (MIC) behavior of carbon steel is investigated in the presence of Vibrio and Pseudomonas. Sterilized natural seawater inoculated with Pseudomonas, Vibrio, and the mixture of Pseudomonas and Vibrio, separately, and they are utilized as the media for corrosion characterizations, which are closer to the natural environment in seawater. Weight loss measurements, electrochemical techniques (the open-circuit potential, electrochemical impedance spectroscopy (EIS), and potentiodynamic polarization curves), and surface analysis (scanning electron microscopy (SEM)) are performed to explore the synergistic effect of Pseudomonas and Vibrio on the corrosion behavior of carbon steel. As seen from the growth curves of bacteria, the growth and propagation of Pseudomonas and Vibrio are affected by their metabolic activities. Besides, the results obtained by SEM show that more severe pitting corrosion is observed on the coupons exposed to the sterilized natural seawater inoculated with the mixture of Pseudomonas and Vibrio. Further, the results from electrochemical measurements and weight loss measurements suggest that under the synergistic effect of Pseudomonas and Vibrio, the initial corrosion rate of carbon steel is inhibited, while the latter corrosion is enhanced.
Community Distribution of Biofilms along a Vertical Wellbore in a Deep Injection Well during Petroleum Production
Résumé : In petroleum production, microbial investigations are essential for microbial-induced corrosion (MIC) control and enhanced oil recovery (EOR) processes. It is suggested that microorganisms can attach to the inner wall of pipes as biofilms, which are more stable and could cause more serious corrosion than planktonic microorganisms in the water phase. At present, research on the biofilms during oil production is mainly focused on the surface pipelines, while few reports have directly investigated biofilms in vertical deep wells. Therefore, in this study, wellbore biofilms were sampled during well workover from several well-tube segments corresponding to different original depths (approximately 0, 840, and 1330 m). The injected water was sampled as well. The results of the 16S rRNA gene library sequencing showed that the biofilms and water-phase communities were distinct (dissimilarity of 0.56–0.64), although they shared 64 OTUs. At the phylum level, the relative abundance of Proteobacteria was 74.65% in the water phase and only 7.86–27.41% in the biofilms. The dominant phylum, Firmicutes, was 6.03–41.21% in the three biofilms, while only 1.16% in the water phase. With increasing depth, the biofilm communities became more diverse (Shannon index of 3.43–4.21), more anaerobic, and more thermophilic possibly due to the depleting oxygen and increasing temperature in samples from the deeper well. For instance, the relative abundance of anaerobes (archaea and strict anaerobic bacteria) in biofilms increased from 18.32 to 40.53%. Thermophilic bacteria (such as Kosmotoga) increased from 6.65 to 15.82%. Among methanogens, hydrogenotrophic genera (such as Methanobacterium and Methanolinea) increased from 3.66 to 9.68%. This study revealed the structural differences between water-phase and biofilm communities in the well, and the depth-dependent distribution of the biofilm communities. These results improved the understanding of microbial ecology in wellbores, which will benefit microbial activity control measures applied in oil production processes, including MIC and oil recovery.
Effect of different disinfection treatments on the adhesion and separation of biofilm on stainless steel surface
Résumé : Attachment and separation of sulfate reducing bacteria (SRB) biofilm on stainless steel (SS) in simulated cooling water with and without different sterilization treatments was investigated by calculation of surface energy, theoretical work of adhesion and analysis of Scanning Electron Microscope/Energy Dispersive Spectrometer. Two types of biocides, glutaraldehyde and Polyhexamethylene guanidine (PHMG), and electromagnetic treatment were used in this paper. The results show that PHMG had the best bactericidal performance, followed by glutaraldehyde, and electromagnetic treatment was the lowest one. The theoretical work of adhesion was used to quantitatively evaluate the adhesion of biofilm on the surface of the metal. Theoretical work of adhesion between biofilm and SS in simulated cooling water increased with time. The theoretical adhesion work and adhesive capacity of biofilm to SS surface increased after treating with glutaraldehyde while decreased after treating with PHMG and electromagnetic field. As the theoretical adhesion work decreased, the biofilm was gradually removed from the stainless steel surface. On the contrary, the biofilm adhered more firmly. The results of SEM were also consistent with the calculation results of theoretical adhesion work. The results obtained indicated that electromagnetic treatment had the lowest effect in sterilization but the best in biofilm separation.
Reducing Emerging Contaminants Ensuing from Rusting of Marine Steel Installations
Résumé : Marine steel installations are usually subject to biocorrosion due to their immersing in seawater. Biocorrosion-causing microorganisms, such as bacteria and fungi, often form biofilms on materials, inducing chemical changes in these materials and in the surrounding liquid medium. The formed biofilms resulting from this phenomenon are considered as emerging contaminants. In this work, in addition to the realization of the electrodeposition of zinc on a steel in chloride bath with various concentrations of Taxus baccata extracts as additives using a direct courant supply, the study of the corrosion of the obtained substrates was performed in seawater as an aggressive environment. The efficiency against corrosion was evaluated by potentiodynamic polarizations and weight loss measurements. The coated surface morphology was analyzed using brightness meter, thickness meter and adhesion tests. The experimental results showed that all tested extracts performed the quality of the zinc deposits and their efficiency against corrosion indicating that coated samples in the presence of the extracts were more resistant minimizing the emerging contaminants in seawater.
Responses of soil microbiome to steel corrosion
Résumé : The process of microbiologically influenced corrosion (MIC) in soils has received widespread attention. Herein, long-term outdoor soil burial experiments were conducted to elucidate the community composition and functional interaction of soil microorganisms associated with metal corrosion. The results indicated that iron-oxidizing (e.g., Gallionella), nitrifying (e.g., Nitrospira), and denitrifying (e.g., Hydrogenophaga) microorganisms were significantly enriched in response to metal corrosion and were positively correlated with the metal mass loss. Corrosion process may promote the preferential growth of the abundant microbes. The functional annotation revealed that the metabolic processes of nitrogen cycling and electron transfer pathways were strengthened, and also that the corrosion of metals in soil was closely associated with the biogeochemical cycling of iron and nitrogen elements and extracellular electron transfer. Niche disturbance of microbial communities induced by the buried metals facilitated the synergetic effect of the major MIC participants. The co-occurrence network analysis suggested possible niche correlations among corrosion related bioindicators.
Specific Features of Biocorrosion of the Circulation Cooling System in the Petrochemical Industry
Résumé : The circulating water of the cooling systems of petrochemical enterprises has a number of special features: the temperature of cooling water is in the range of 14-28 ºС all year round, the evaporation of water in cooling towers increases the concentration of dissolved salts. Inevitable ingress of hydrocarbons, dosing of corrosion inhibitors, scaling, reagents for dispersing and softening of the water creates favorable conditions for micro- and macroorganisms development. Existing standards stipulate that the number of viable bacterial cells in planktonic form should not exceed 10 cells/ml, the number of bacteria in the adhered form is not regulated, nevertheless these organisms in particular lead to biocorrosion. During the assessing of the biological degradation of water cycle equipment materials, it was studied the micro- and macroorganisms that populate the surface of steel samples 20. Studies of the effect of this bacteria on the corrosion of steel 20 showed that this whole complex of micro- and macroorganisms, releasing metabolites into the water, also indirectly affects the processes of corrosion, and when choosing protection methods, it is necessary to take into account not only the presence and types of bacteria, but also the entire local biocenosis.
A Review of Graphene-Based Materials for Marine Corrosion Protection
Résumé : Graphene-based anti-corrosion materials exhibit excellent chemical inertness and impermeability and are promising and emerging materials for the protection of metals. In this review, the recent progress in the production of graphene-based materials for protection against marine corrosion is discussed. Major mechanisms of marine corrosion and strategies for corrosion protection are illustrated. The properties and methods used for the preparation (micromechanical stripping method and chemical vapor deposition) of graphene are introduced. Two fabrication strategies for graphene-based corrosion protection materials are presented. For pure graphene films, fewer defects and low conductivity lead to the enhancement of anti-corrosion properties. For graphene composite coatings, improving the dispersibility of graphene in the coating matrix and strengthening the durability render graphene coatings to be more effective for marine corrosion protection. Insulation is highly desirable for avoiding electrochemical reactions to protect against heavy marine corrosion in the later stages. Finally, we provide perspectives on the future of graphene-based materials for marine corrosion protection, anticipating that a properly prepared graphene composite coating can serve as a long-term anti-corrosive material for marine applications.
Inhibiting corrosion of aluminum alloy 5083 through Vibrio species biofilm
Résumé : Microbiologically influenced corrosion inhibition (MICI) of aluminum alloy (AA) 5083 by three representative Vibrio species were evaluated using electrochemical, surface analysis and surface characterization techniques. Interestingly, all the bacteria exhibited profound inhibitory effect on the corrosion of AA5083 in the chloride-containing culture medium. The MICI mechanism of tested Vibrio species is that mature biofilms acted as a diffusion barrier to prevent the penetration of corrosive chloride and consumed up the diffused oxygen by their aerobic respiration. Thus, the biofilm increased the passive range and inhibited the localized attack on the AA5083 surfaces.
Corrosion Analysis of AISI 430 Stainless Steel in the presence of Escherichia coli and Staphylococcus aureus
Résumé : AISI 430 stainless steel is an attractive material to be used in the healthcare industry, particularly as a sensor due to its low cost, corrosion resistance, as well as being Ni-free. AISI 430 was evaluated in an artificial sweat solution with the presence of Escherichia coli, and Staphylococcus aureus. Surface microbial analyses did not reveal colonization of bacteria on metallic surfaces, even when bacteria adhesion was investigated in a Müeller-Hinton solution. However, by electrochemical techniques, the AISI 430 surfaces demonstrated clear signs of corrosion mainly in a sterile medium after two weeks of exposure.
A study of bacteria adhesion and microbial corrosion on different stainless steels in environment containing Desulfovibrio vulgaris
Résumé : Stainless steel is an important material used in many applications due to its mechanical strength and corrosion-resistant properties. The high corrosion resistance of stainless steel is provided by the passive film. Different stainless steels have different alloy elements and surface properties which could have a significant influence on bacterial attachment to the surface and thus might result in different microbial corrosion behaviours. In this study, the effect of adhesion of sulfate-reducing bacteria (SRB) on corrosion behaviour in artificial seawater on different stainless steels was investigated. Stainless steel materials used were SS 410, SS 420, SS 316 and DSS 2205 and pure chromium. The contact angle was measured to study the effect of surface properties of materials. Adhesion was measured by counting cells attached to the surface of materials. The corrosion behaviour of the materials was measured by electrochemical testing including measuring open circuit potential, electrochemical impedance spectroscopy and potentiodynamic behaviour. The long-term corrosion behaviour of each material was studied after six months of exposure by measuring weight loss and surface analysis with scanning electron microscope with energy-dispersive X-ray analysis. Hydrophobicity had a strong effect on bacterial attachment. Alloying elements e.g. nickel also had shown its ability to attract bacteria to adhere on the surface. However, the corrosion rate of different materials is determined not only by bacterial attachment but also by the stability of the passive film which is determined by the alloying elements, such as Mo and Cr. Chromium showed high resistance to corrosion, possibly due to toxicity on bacterial attachment. The nature of bacterial attachment and corrosion behaviour of the materials are discussed.
Effect of Cathodic Polarization on Corrosion Behavior of X65 Steel in Seawater Containing Iron-oxidizing Bacteria
Résumé : Microbiologically influenced corrosion is mainly caused by the biological activity in the biofilm, which clearly illustrates the role of attached bacteria in the form of biofilm in initiating or accelerating corrosion. Although it has been proven that electrochemical methods can prevent the formation of biofilms on metal surfaces, the special effect of cathodic polarization in bacterial attachment and growth is still inconclusive. The purpose of this work was to investigate the effect of cathodic polarization on the attachment of iron-oxidizing bacteria (IOB) in seawater during the initial stage of biofilm formation. Results showed that under the polarization potential of −1050 mV vs. SCE, IOB attachment and biofilm growth were well controlled. Further, the potential of −1050 mV vs. SCE exhibited more effective inhibitory effect on IOB-induced pitting corrosion than that of −700 mV vs. SCE, which was related to the accumulation of electrons on the metal surface during cathodic polarization. The cathodic potential of −1050 mV vs. SCE also altered the electrochemical parameters at the metal-biofilm interface, such as the increase of pH and the formation of protective calcareous deposits, which contributed to protect the metal from IOB-induced corrosion.
Assessment of bio-corrosion inhibition ability of Hafnium based cationic metallosurfactant on iron surface
Résumé : Hafnium based metallosurfactant has been evaluated as a greener and novel corrosion inhibitor for iron in saline and microbial conditions. A facile approach has been targeted by preparing Hafnium based surfactant bishexadecylpyridinium hafnium hexachlorate (HfCPC) using low cost ligand insertion method with easy work up procedure. The aggregation behaviour and antimicrobial activity of HfCPC against marine vibrio Halobacterium salinarium and Halococcus morrhuae were assessed. Electrochemical techniques were applied to check the dynamic corrosion process and inhibition efficiency. UV–vis spectroscopy, FE-SEM, XPS, contact angle goniometry were employed to grow mechanistic insight into inhibition behaviour. KI shows the synergistic inhibitory action with HfCPC.
Tetrakis hydroxymethyl phosphonium sulfate (THPS) with biopolymer as strategy for the control of microbiologically influenced corrosion in a dynamic system
Résumé : In this study, satisfactory efficacy was found from the combination of the biocide THPS with the xanthan biopolymer for the control of microbiologically influenced corrosion in SAE 1010 carbon steel. The effectiveness of this combination was compared with three systems: without treatment and using THPS and xanthan in isolation. The experiments were carried out in a turbulent flow looping, in which the circulating medium was seawater. Quantification of microbial groups, corrosion rate measurements through mass loss, quantification of biomass and extracellular polymeric substances (EPS) of the biofilm were performed. The biofilm on the coupons was analyzed using the scanning electron microscope (SEM). X-Ray Diffraction (XRD) was used to identify the crystallographic phases of the corrosion products. The results showed that, even with low concentration of xanthan added, the THPS + xanthan system had a greater reduction of microbial groups in relation to the other systems. This combination reduced biomass and extracellular polymeric substances. Despite the presence of grooves, SEM indicated that xanthan forms a more adherent film on steel due to its dispersant property. Lepidocrocite phase was not found in the corrosion products from systems with THPS, whereas mackinawite phase was found.
Biocorrosion caused by microbial biofilms is ubiquitous around us
Résumé : Biocorrosion first surfaced in the scientific literature
when Richard H. Gaines associated corrosion with
bacterial activities in 1910. It is also known as
microbiologically influenced corrosion (MIC). In general,
it covers two scenarios. One is that microbes
cause corrosion directly, which usually means
microbes secrete corrosive metabolites or microbes
harvest electrons from a metal for respiration to
produce energy. In the second scenario, microbes
are behind the initiation or acceleration of corrosion
caused by a pre-existing corrosive agent such as
water and CO2, by compromising the passive film
(often a metal oxide film on a metal). MIC is caused
by microbial biofilms. It is everywhere around us.
This work dissects some notable examples with
perspectives.
Mitigation of eco-unfriendly and costly microbial induced corrosion using novel synthesized Schiff base cationic surfactants
Résumé : BACKGROUND Sulfate-reducing bacteria (SRB) are considered to be the major cause of microbial-induced corrosion. It contributes to many environmental and other costly industrial problems in the petroleum industry. Thus there is always a great need for producing new efficient biocides and biocorrosion inhibitors. RESULTS In this work, three Schiff base surfactants (coded Q12, Q14 and Q18) were synthesized and characterized using Fourier transform infrared and 1H-nuclear magnetic resonance techniques. A mixed culture of SRB was collected from an oil field production tank located at the North Bahrya Petroleum Company (NORPETCO), Egypt. The antimicrobial effect of the newly synthesized surfactants was studied against sessile and planktonic SRB over their different growth phases by various methods: viable cell count via most probable number method, estimation of biogenic sulfide concentrations, weight loss of iron coupons in microbial growth medium and biofilm examination on coupon surfaces using scanning electron microscopy. The synthesized surfactants expressed a high inhibition effect on bacterial growth, recording a minimum inhibitory concentration of 750 mg L−1 for Q18 and 1000 mg L−1 for both Q12 and Q14, with a considerable decline in biogenic sulfide productivity from a dose of 500 mg L−1 until complete suppression at a dose of 1000 mg L−1. Also the synthesized surfactants showed an effective metal corrosion inhibition at a concentration of 500 mg L−1. CONCLUSION Schiff base cationic surfactants with long hydrophobic chains can be recommended as biocorrosion inhibitors for industrial application in the petroleum sector. © 2020 Society of Chemical Industry (SCI)
Desulfovibrio and Pseudomonas Dominated Enriched Produced Water Reinforcing their Importance in Oilfields and Production Processes
Résumé : Enrichment based isolation methods and molecular identification were used to investigate the microbial communities in produced water obtained from Periquito (PQO) and Galo de Campinas (GC) onshore oilfields in Brazil. Produced water was enriched with Postgate B, Postgate C and Baars media and incubated. DNA was extracted, PCR amplified and16S rDNA fragments were sequenced using Illumina TruSEq. 4.2 million reads were analysed and deposited at the Sequence Read Archive at NCBI. No significative differences in microbial community composition could be attributed to the enrichment but significant differences were observed from two oil fields. The dominant Bacterial Orders detected from both oilfields were Desulfovibrionales, Pseudomonadales and Enterobacteriales. Pseudomonas were found predominantly in Periquito oilfield (19.8%) with only 2,4% at Galo de Campinas. Pleomorphominas (3.76%) and Shewanella (4,69%) were exclusive to and possible biomarkers for the Periquito Oilfield. 11.05% and 7.62% of the sequences were not classified at genus level and detected at GC and P. Abundances changed for Desulfovibrio from P, 29.8% at PQO and 16.08% at GC. The Clostridium _sensu_stricto varied from 2.8% at PQO and 2.4% at GC). Pseudomonas were found predominantly in Periquito oilfield (19.8%) with only 2,4% at Galo de Campinas.
Pleomorphominas (3.76%) and Shewanella (4,69%) were almost exclusive to and possible biomarkers for the Periquito Oilfield. These data provide a bacterial biodiversity benchmark for future produced water treatment and microbially enhanced oil recovery (MEOR).
Microbiologically Induced Corrosion of Duplex Stainless Steel
Résumé : Microbiologically Influenced Corrosion (MIC) has been known to cause serious environmental problems and significant economic loss. Chlorella Vulgaris is a type of algae found in both freshwater and marine environments and has been widely connected with steel corrosion and biofouling. Duplex stainless steels (DSS), widely used in oil industries and marine environments, suffers pitting corrosion due to MIC. A recent mitigation approach employed magnetic fields. A possible mechanism is the field-assisted development of a passivation layer that reduced corrosion. Thus, the effects of both microbial culture and magnetic fields related to the corrosion of the samples creates unexplored areas of interest. The MIC behavior of 2205 DSS with and without the influence of a magnetic field was investigated inside the cultured media of chlorella vulgaris. The cell densities and mass loss measurements of chlorella vulgaris were calculated after 1,3,5, and 7 days.
Inhibition of microbial souring with molybdate and its application under reservoir conditions
Résumé : Souring induced by sulfate reducing microorganisms (SRM) represents a severe problem in the petroleum industry. In addition to conventional biocides and nitrate, alternative SRM inhibitors such as molybdate have been proposed recently for controlling microbial souring. We used oilfield-derived microbial consortia, rock and fluids to test molybdate as a specific SRM inhibitor for a microbial enhanced oil recovery (MEOR) application where souring might occur as a side effect. SRM cells were quantified and dissolved molybdate, sulfate and gaseous hydrogen sulfide were measured under different dynamic conditions in sandpacks with and without residual oil. In batch experiments, 0.5 mM molybdate inhibited SRM growth whereas hydrogen sulfide and mineral precipitations were observed in bottles amended with 100 mM nitrate. However, significant molybdate adsorption onto reservoir rock occurred and maximum Langmuir saturation was estimated to be ≥ 34 μmol g−1. Residual oil allowed a further propagation of molybdate into sandpacks, but a pH < 6 and sulfide concentrations >11 μMH2S aq limited the efficiency of molybdate due to rapid adsorption. Under favorable souring conditions, we also observed the localized formation of macroscopic iron sulfide precipitations. These resulted in a four-fold permeability decrease after the injection of SRM substrates for 40 days and a calculated mean sulfate reduction rate of 52 μM h−1. However, delayed sulfate reduction in molybdate-preflushed sandpacks suggests an inhibitory effect even if molybdate is partially adsorbed. Sulfate reduction was not detected when molybdate was continuously injected with MEOR nutrients into sandpacks demonstrating its inhibitory efficiency in case it is applied in early phases of field operations with a potential risk of souring.
Electron transfer mediator PCN secreted by aerobic marine Pseudomonas aeruginosa accelerates microbiologically influenced corrosion of TC4 titanium alloy
Résumé : Titanium alloys possess excellent corrosion resistance in marine environment, thus the possibility of its corrosion caused by marine microorganisms are fully neglected. In this work, microbiologically influenced corrosion (MIC) of TC4 titanium alloy caused by marine Pseudomonas aeruginosa was investigated through electrochemical and surface characterizations during a 14-day immersion test. Results revealed that the unstable surface caused by P. aeruginosa resulted in exposure of Ti2O3 and severe pitting corrosion with maximum pit depth of 5.7 μm after 14 days of incubation. Phenazine-1-carboxylate (PCN), secreted by P. aeruginosa, promoted the extracellular electron transfer (EET) and accelerated corrosion. Deletion of the phzH gene, which codes for the enzyme that catalyzes PCN production, from the P. aeruginosa genome, resulted in significantly decreased rates of corrosion. These results demonstrate that TC4 titanium alloy was not immune to marine MIC, and EET was responsible for the corrosion of TC4 titanium alloy caused by P. aeruginosa.
Sulfate reducing bacterium Desulfovibrio vulgaris caused severe microbiologically influenced corrosion of zinc and galvanized steel
Résumé : The microbiologically influenced corrosion (MIC) of zinc and galvanized steel caused by a sulfate reducing bacterium (SRB) was investigated. After 7 days of incubation of Desulfovibrio vulgaris in 125 mL anaerobic vials (100 mL culture medium) at 37 °C, the sessile cell coverage on the galvanized steel was slightly higher than that on pure zinc: (1.9 ± 0.2) × 109 cells/cm2 vs. (9.0 ± 1.8) × 108 cells/cm2. The weight losses for galvanized steel and pure zinc were 31.5 ± 2.5 mg/cm2 and 35.4 ± 4.5 mg/cm2, respectively, which were 101 higher than that for carbon steel. The corrosion current densities of galvanized and pure zinc were 25.5 μA/cm2 and 100 μA/cm2, respectively after the 7-day incubation, confirming that galvanized steel was less prone to SRB MIC despite having a slightly higher sessile cell count. In both cases, the corrosion product was mainly ZnS. Three MIC mechanisms were possible for the severe corrosion against the two metals. Extracellular electron transfer MIC (EET-MIC) was thermodynamically favorable for zinc. Furthermore, in the presence of Zn coupons, H2 evolution in the headspace was 5.5 times higher than without Zn coupons, which suggested that proton attack and/or H2S attack also occurred in the corrosion process.
Long-term souring treatment using nitrate and biocides in high-temperature oil reservoirs
Résumé : The biogenic production of hydrogen sulfide (H2S) by sulfate-reducing bacteria (SRB) and consequently the souring of reservoirs are still major problems in oil industry. Biocides and/or nitrate are used to control SRB activity in oil reservoirs, but long-term studies are still needed to prove their efficacy. In this study, two high-temperature (80–84 °C) oil reservoirs were analyzed over three years. Nitrate and tetrakishydroxymethyl phosphonium sulfate (THPS) were added to the water injection system (WI) at the beginning of secondary oil recovery in oil reservoir 1, while nitrate was only added 19 months after the beginning of secondary oil recovery in oil reservoir 2. The H2S concentration was quantified monthly in production wells, and the total bacterial community (based on the gene coding for 16S rRNA) and SRB (based on dsrA and apsAB genes) were determined using fluorescence in situ hybridization (FISH) and PCR-DGGE analyses. Nitrate plus THPS controlled H2S production for 34 months in oil reservoir 1. THPS injection in oil reservoir 2 controlled H2S levels for 17 months, and the further addition of nitrate in water injection did not control H2S production. PCR-DGGE analyses and the molecular identification of the dominant groups showed a predominance of thermophilic bacteria, including different SRB (such as Desulfocaldus and Desulfonauticus) and nitrate-reducing bacteria (NRB – Marinobacter) in oil reservoir 1 and mesophilic SRB (Desulfovibrio) and NRB (Halomonas and Acinetobacter) in oil reservoir 2. The strategy chosen during secondary oil recovery modulated the microbial community and, consequently, changed the dynamics of H2S production.
The differences in the corrosion product compositions of Methanogen-induced microbiologically influenced corrosion (Mi-MIC) between static and dynamic growth conditions
Résumé : Currently, corrosion rates (CR) and/or corrosion products (CP) obtained for methanogen-induced microbiologically influenced corrosion (Mi-MIC) on carbon steel are mainly analyzed from static-incubations. By using a multiport-flow-column, much higher CRs (0.72 mm/yr) were observed, indicating static-incubations are not suitable for determining the corrosive potential of Mi-MIC. With the combination of various analytical methods (ToF-SIMS/SEM-EDS/SEM-FIB) and contrary to previously published data, we observed that CPs contained phosphorus, oxygen, magnesium, calcium and iron but lacked carbon-related species (e.g. siderite). Overall, siderite nucleation is disrupted by methanogens, as they convert aqueous bicarbonate into carbon dioxide for methanogenesis resulting in increased localized corrosion.
Novel Mode of Molybdate Inhibition of Desulfovibrio vulgaris Hildenborough
Résumé : Sulfate-reducing microorganisms (SRM) are found in multiple environments and play a major role in global carbon and sulfur cycling. Because of their growth capabilities and association with metal corrosion, controlling the growth of SRM has become of increased interest. One such mechanism of control has been the use of molybdate (MoO42-), which is thought to be a specific inhibitor of SRM. The way in which molybdate inhibits the growth of SRM has been enigmatic. It has been reported that molybdate is involved in a futile energy cycle with the sulfate-activating enzyme, sulfate adenylyl transferase (Sat), which results in loss of cellular ATP. However, we show here that a deletion of this enzyme in the model SRM, Desulfovibrio vulgaris Hildenborough, remained sensitive to molybdate. We performed several subcultures of the sat strain in the presence of increasing concentrations of molybdate and obtained a culture with increased resistance to the inhibitor (up to 3 mM). The culture was re-sequenced and three single nucleotide polymorphisms (SNPs) were identified that were not present in the parental strain. Two of the SNPs seemed unlikely candidates for molybdate resistance due to a lack of conservation of the mutated residues in homologous genes of closely related strains. The remaining SNP was located in DVU2210, a protein containing two domains: a YcaO-like domain and a tetratricopeptide-repeat domain. The SNP resulted in a change of a serine residue to arginine in the ATP-hydrolyzing motif of the YcaO-like domain. Deletion mutants of each of the three genes apparently enriched with SNPs in the presence of inhibitory molybdate and combinations of these genes were generated in the Δsat and wild-type strains. Strains lacking both sat and DVU2210 became more resistant to molybdate. Deletions of the other two genes in which SNPs were observed did not result in increased resistance to molybdate. YcaO-like proteins are distributed across the bacterial and archaeal domains, though the function of these proteins is largely unknown. The role of this protein in D. vulgaris is unknown. Due to the distribution of YcaO-like proteins in prokaryotes, the veracity of molybdate as a specific SRM inhibitor should be reconsidered.
Microbial biofilm monitoring by electrochemical transduction methods
Résumé : The negative impact of biofilms in both the industry and the human health, demands the development of strategies for the in situ and early detection of biofilm formation. In this review we describe potentiometric, voltammetric and impedance-based sensors as to provide an overview of the different electrochemical techniques applied in biofilm detection and monitoring.
The Impact of Temperature, Chlorides, and SRB on the Corrosion of Carbon Steel in Soil
Résumé : This investigation aimed to study the corrosion performance of low carbon steel in a soil environment at different temperatures. The steel specimens in soil were treated at three temperatures: 5°C, 25°C and 60°C. The specimens were embedded in the chloride-free soil for 21 days and then 3.5 % (by weight) NaCl was added to the soil. The specimens were then kept in the chloride-contaminated soil for 54 days. The results of electrochemical experiments showed superior corrosion performance of the specimens at 60°C had lowest corrosion activity, followed by the specimens at 5°C and 25°C. The slow nature of the kinetics of the corrosion reactions at 5°C compared to the ambient temperature was the reason for this improvement at 5°C. A lower number of micro-organisms including sulfate-reducing bacteria (SRB) in the soil at 60°C compared to the other temperatures was attributed to the lower corrosion activity of steel in soil at 60°C compared to the steel in the soils at other temperatures.
Microbial influenced corrosion of processing industry by re-circulating waste water and its control measures - A review
Résumé : In this review article, illustrating the impact and fundamental stuff of microbially influenced corrosion (MIC) along with mechanism, maintenance of materials, human life, wellbeing and inhibitors for cooling towers. Corrosion is a natural mechanism of oxidation and reduction of metal ions by chemical and electrochemical processes and microorganism accumulation. MIC occurs through the aggregation of microbes which can be secreting the extra polymeric substances (EPS) that oxidation of the metal surface. According to the reviews, in the cooling water system, the corrosion begins in the anode charge because its oxidation reaction quickly takes place on the metal surface than the cathode charge. Annihilate the corrosion process needs certain helper substances such as chemical or green compounds, called inhibitors. Corrosion inhibitors typically adopt the adsorption mechanism due to the presence of organic hetero atoms. Chemical and green inhibitors are used to prevent corrosion processes and since ancient times, vast quantities of chemical inhibitors have been used in industry due to their effectiveness and consistency. But still, the chemical inhibitors are more toxic to humans and the environment. Instead of chemical inhibitors, green inhibitors (natural products like plant leaves, flowers, stem, buds, roots and sea algae) are developed and used in industries. Generally, green inhibitors contain natural compounds, high inhibition efficiency, economic, eco- and human-friendly, and strong potential features against corrosion. Thus, a lot of research is ongoing to discover the green inhibitors in various parts of plants and seaweeds.
Study on Microbial Corrosion Resistance of Ni-P-Ag Coatings in Artificial Marine Environments Containing Sulphate-reducing Bacteria
Résumé : In this paper, silver was electroless-plated onto nickel-phosphorus (Ni-P) to improve its microbial corrosion resistance. The microbial corrosion behaviour of nickel-phosphorus-silver (Ni-P-Ag) in artificial marine environments with Desulfovibrio desulfuricans was experimentally investigated. Fluorescence microscopy (FM), scanning electron microscopy (SEM), and X-ray fluorescence (XRF) were used to analyse the colonization of sulphate-reducing bacteria (SRB). The results indicate that Ni-P-Ag could not inhibit the growth of SRB, which were still able to proliferate wihin a short period. Based on the electrochemical impedance spectroscopy (EIS) results, the potentiodynamic curves of Ni-P-Ag were concentrated from 1 d to 31 d with almost no shift in the negative direction. The corrosion potentials and lgIcorr of the Ni-P-Ag potentiodynamic curves changed slowly. The Nyquist and Bode plots of Ni-P-Ag coating in seawater containing SRB were both relatively stable. According to the equivalent circuits, the Rct of Ni-P-Ag decreased slowly from 5.75 kΩ·cm-2 to 2.35 kΩ·cm-2. The results showed that the microbial corrosion resistance of silver coating is obvious. Although silver coating could not inhibit SRB reproduction, Ni-P-Ag can effectively resist SRB corrosion.
Effect of Applied Potential on Stress Corrosion Cracking Behavior of X80 Steel in Alkaline Soil Simulated Solution with Sulfate-reducing Bacteria
Résumé : In this study, the effect of applied potential on stress corrosion behavior of X80 pipeline steel in Dagang soil containing sulfate-reducing bacteria was comprehensively analyzed by means of the AC impedance technique and slow strain-rate tensile tests and scanning electron microscope observation of fracture morphology. The results indicate that, with decreasing electrode potential, the corrosion degree of the sample first decreases and then increases, and the stress corrosion cracking sensitivity exhibits a certain rule. Under the Ecorr and a potential of -725 mV(vs.CSE), the stress corrosion cracking mechanism of metal is anodic dissolution. The synergistic effect of sulfate-reducing bacteria and stress results in the initiation and propagation of cracks on the surface of the metal electrode. At -1275 mV(vs.CSE), the mechanism of stress corrosion cracking is hydrogen-induced cracking. The sulfate-reducing bacteria exacerbates the cathodic hydrogen evolution at this potential. Under the combined effects of hydrogen and stress, stress corrosion cracking behavior occurs in metals.
Myrtus communis extract : a bio-controller for microbial corrosion induced by sulphate reducing bacteria
Résumé : This study aimed to study the inhibitory effect of the Myrtus communis extract on the microbiologically influenced corrosion (MIC) induced by sulphate reducing bacterial (SRB) consortium in the cooling tower water. The SRB consortium was grown on the surface of the st37 steel and its effects on the surface corrosion were evaluated. The results of electrochemical measurements and microscopic observations revealed that the extract could significantly reduce the corrosion by inhibiting the SRB biofilm formation. The addition of the 0.781 mg ml−1 of the extract into the SRB medium led to a considerable reduction (about seven times) in the corrosion process of the st37 steel and kept it at an almost constant value. Based on Gas chromatography-mass spectrometry analysis, 2-Furancarboxaldehyde, 5-(hydroxymethyl) (42.396%) was the most abundant compound identified in the plant extract. The molecular identification has proved that most population of SRB consortium was related to Desulfovibrio vulgaris species.
Development of a Rapid Method for Monitoring Biodeterioration of Petroleum Products and Technical Fluids. Part I.
Résumé : Principles of a rapid method for monitoring biodeterioration of technical fluids were developed with metalworking fluids as examples. Physicochemical and operation properties of spent metalworking fluids were considered. The loss of the biological resistance of metalworking fluids leads to irreversible changes in the physicochemical and operation properties. A bank of test microorganisms required for validating the rapid method for monitoring biodeterioration was compiled.
Plus de références Biocorrosion
• Antifouling
Spray-Painted Hydrogel Coating for Marine Antifouling
Résumé : Biofouling is a longstanding problem for biomedical devices, food storage, and marine equipment. Traditional antifouling strategies involve the use of biocidal agents, low surface-energy surface, and nanopatterned coatings. Recent studies show that hydrophilic surfaces are also promising for antifouling by directly reducing the adhesion of proteins and polysaccharides. However, it remains challenging to stably and conveniently coat nonadhesive hydrophilic polymers to various surfaces in high density. Especially, for marine antifouling, large-area painting of hydrophilic polymer coatings is susceptible to low adhesion strength, inhomogeneous surface coverage, and short durability. Here, a paintable antifouling hydrogel coating is proposed to overcome these limitations. An epoxy midcoat layer is introduced to provide both strong noncovalent adhesion to various surfaces and covalent linkages to hydrogel layers. The 3D hydrogel layers provide homogenous, relatively low Young's modulus and dense surface coverage and therefore shows outstanding antifouling properties toward various proteins, polysaccharides, seaweeds, and oil. Moreover, this hydrogel coating degrades slowly in sea water and facilitates the release of fouling biomolecules and organisms. Considering the great antifouling and fouling release properties, convenient coating processes, and high adhesion strength, this novel paintable antifouling hydrogel coating is anticipated to be broadly applicable for marine antifouling and other relevant fields.
The effect of ultrasonic antifouling control on the growth and microbiota of farmed European sea bass (Dicentrarchus labrax)
Résumé : Biofouling is a serious threat to marine renewable energy structures and marine aquaculture operations alike. As an alternative to toxic surface coatings, ultrasonic antifouling control has been proposed as an environmentally friendly means to reduce biofouling. However, the impact of ultrasound on fish farmed in offshore structures or in marine multi-purpose platforms, combining renewable energy production and aquaculture, has not yet been assessed. Here we study the impact of ultrasound on the growth and microbiota of farmed European sea bass (Dicentrarchus labrax) under laboratory conditions. Whereas growth and survival were not reduced by ultrasound exposure, microbiological analysis using plate counts and 16S rRNA gene based metataxonomics showed a perturbation of the gill and skin microbiota, including an increase in putative pathogenic bacteria. This warrants further research into the long-term effects of ultrasonic antifouling control on the health and wellbeing of farmed fish.
20 - Marine applications
Résumé : This chapter mainly emphasizes on the recent advancement in polysaccharide-based materials development in the large variety of marine applications such as wastewater treatment, corrosion inhibitors, drag reducer, antifouling agents, and in marine polymer coatings. Owing to the intrinsic properties of polysaccharide, functionalization of chitin, chitosan with metal nanoparticles for identification of the toxic ions present in the marine water by chemical and electrochemical methods are explored. The different separation methods for the removal of toxic ions and classification of the different types of polysaccharides were discussed in detail. Strategies toward the development of anticorrosive materials by natural and synthetic polysaccharides with different formulation were screened as marine polymer coatings in detail, pointing out their salt spray resistance, ionic conductivity, and prospective applications.
Acute and chronic effects of innovative antifouling nanostructured biocides on a tropical marine microcrustacean
Résumé : This study aimed to investigate the toxicity of innovative antifouling nanostructured biocides DCOIT and silver associated to silica nanocapsules (SiNC) on the tropical microcrustacean Mysidopsis juniae. The toxicity of the tested compounds can be summarized as follows (acute tests): DCOIT > SiNC-Ag > SiNC-DCOIT > SiNC-DCOIT-Ag > SiNC > Ag; (chronic tests): SiNC-Ag > SiNC-DCOIT-Ag > DCOIT > Ag > SiNC, although it was not possible to determine the chronic toxicity of SiNC-DCOIT. In general, our data demonstrated that mysids were more sensitive than most temperate species, and it was possible to conclude that the combination SiNC-DCOIT-Ag showed less acute toxicity in comparison to the isolated active compounds, reinforcing data obtained for species from temperate environments on the potential use of nanomaterial to reduce toxicity to non-target species. However, despite representing less risk to the environment, the compound SiNC-DCOIT-Ag is still very toxic to the non-target tropical mysid.
Toward the Application of Graphene for Combating Marine Biofouling
Résumé : The discovery of graphene has brought great innovations to materials science. Since tributyltin antifouling coatings were banned worldwide in 2008, the development of green antifouling coatings has become necessary. Recently, novel graphene-related antifouling coatings have been the focus of many studies due to their enhanced mechanical strength, excellent antifouling capabilities, and environmental friendliness. This review starts by introducing the basic antifouling mechanisms of graphene nanosheets and the possible antifouling mechanisms when graphene is incorporated into coatings. Subsequently, the progress and existing problems regarding the application of graphene in the prevention of marine biofouling are discussed. Specifically, this review focuses on six graphene-related antifouling coatings, including pure graphene film, nanohybrids, foul release coatings, photocatalytic nanocomposites, desalination membranes, and materials for uranium enrichment. The fabrication, antifouling properties, working mechanisms, and future development of graphene-related antifouling coatings are highlighted. In addition, the potential environmental risk of using graphene materials in preventing marine biofouling is explained, and the basic requirements for designing an environmentally friendly graphene-related antifouling coating are discussed. Finally, the prospect of applying graphene materials for combating marine biofouling is presented. This review aims to aid in improving the design of graphene-related green antifouling coatings.
Comparative study for marine antifouling agents based on natural sarcophine product and ZnO nanomaterials
Résumé : Fouling has significant economic influences on sea transportation and other submerged surfaces. This work aims to compare between sarcophine and synthesized ZnO nanospheres as active antifouling ingredients. The two compounds were applied on unprimed steel and were immersed in the seawater of the Eastern Harbour (E.H.), Alexandria, Egypt. Seawater hydrographic parameters were measured. 1H and 13C NMR spectra were carried out to study the structural analysis of sarcophine. ZnO nanospheres were characterized through SEM, XRD, and UV-V instruments. Each of sarcophine and ZnO nanospheres was blended solely by 2% (w/w) with a designed paint formulation of two paint ingredients besides the blank. Duplicate paint formulations were applied on unprimed steel, hanged, and immersed in the E.H. on 30/12/2018. Panels’ surfaces were followed visually and by photographic inspection for fouling succession over different interval times. They lasted for 200 days. Sarcophine showed the least fouled surface by about 15% of tubeworms and barnacles than ZnO or the blank. Most fouling were around the edges of the panel. This is due to its smoother surface, besides it has higher molecular weight than ZnO nano-particles. The hydrographic parameters of the E.H. seawater were within the normal range that these paint formulations are environmentally safe.
Recent Progresses of Superhydrophobic Coatings in Different Application Fields : An Overview
Résumé : With the development of material engineering and coating industries, superhydrophobic coatings with exceptional water repellence have increasingly come into researchers’ horizons. The superhydrophobic coatings with corrosion resistance, self-cleaning, anti-fogging, drag-reduction, anti-icing properties, etc., meet the featured requirements from different application fields. In addition, endowing superhydrophobic coatings with essential performance conformities, such as transparency, UV resistance, anti-reflection, water-penetration resistance, thermal insulation, flame retardancy, etc. plays a remarkable role in broadening their application scope. Various superhydrophobic coatings were fabricated by diverse technologies resulting from the fundamental demands of different fields. Most past reviews, however, provided only limited information, and lacked detailed classification and presentation on the application of superhydrophobic coatings in different sectors. In the current review, we will highlight the recent progresses on superhydrophobic coatings in automobile, marine, aircraft, solar energy and architecture-buildings fields, and discuss the requirement of prominent functionalities and performance conformities in these vital fields. Poor durability of superhydrophobic coating remains a practical challenge that needs to be addressed through real-world application. This review serves as a good reference source and provides insight into the design and optimization of superhydrophobic coatings for different applications.
Mechanical Properties of Protective Coatings against Marine Fouling : A Review
Résumé : The accumulation of marine organisms on ship hulls, such as microorganisms, barnacles, and seaweeds, represents a global problem for maritime industries, with both economic and environmental costs. The use of biocide-containing paints poses a serious threat to marine ecosystems, affecting both target and non-target organisms driving science and technology towards non-biocidal solutions based on physico-chemical and materials properties of coatings. The review reports recent development of hydrophobic protective coatings in terms of mechanical properties, correlated with the wet ability features. The attention is focused mainly on coatings based on siloxane and epoxy resin due to the wide application fields of such systems in the marine industry. Polyurethane and other systems have been considered as well. These coatings for anti-fouling applications needs to be both long-term mechanically stable, perfectly adherent with the metallic/composite substrate, and capable to detach/destroy the fouling organism. Prospects should focus on developing even “greener” antifouling coatings solutions. These coatings should also be readily addressable to industrial scale-up for large-scale product distribution, possibly at a reasonable cost.
Developing New Marine Antifouling Surfaces : Learning from Single-Strain Laboratory Tests
Résumé : The development of antifouling (AF) technology for marine environments is an area of intense research given the severe economic and ecological effects of marine biofouling. Preliminary data from in vitro assays is frequently used to screen the performance of AF coatings. It is intuitive that microbial composition plays a major role in surface colonization. The rationale behind this study is to investigate whether using a mixed population for the in vitro tests yields substantially different results than using single strains during initial screening. A polymeric coating was tested against single- and dual-species cultures of two common microfouler organisms for 49 days. A bacterium (Pseudoaltermonas tunicata) and a cyanobacterium (Cyanobium sp. LEGE 10375) were used in this study. Linear regression analysis revealed that Cyanobium sp. biofilms were significantly associated with a higher number of cells, wet weight, thickness, and biovolume compared to dual-species biofilms. P. tunicata alone had a biofilm growth kinetics similar to dual-species biofilms, although the P. tunicata–Cyanobium sp. mixture developed less dense and thinner biofilms compared to both single-species biofilms. Cyanobium sp. LEGE 10375 biofilms provided the worst-case scenario, i.e., the conditions that caused higher biofilm amounts on the surface material under test. Therefore, it is likely that assessing the AF performance of new coatings using the most stringent conditions may yield more robust results than using a mixed population, as competition between microfouler organisms may reduce the biofilm formation capacity of the consortium.
Spray-Painted Hydrogel Coating for Marine Antifouling
Résumé : Biofouling is a longstanding problem for biomedical devices, food storage, and marine equipment. Traditional antifouling strategies involve the use of biocidal agents, low surface-energy surface, and nanopatterned coatings. Recent studies show that hydrophilic surfaces are also promising for antifouling by directly reducing the adhesion of proteins and polysaccharides. However, it remains challenging to stably and conveniently coat nonadhesive hydrophilic polymers to various surfaces in high density. Especially, for marine antifouling, large-area painting of hydrophilic polymer coatings is susceptible to low adhesion strength, inhomogeneous surface coverage, and short durability. Here, a paintable antifouling hydrogel coating is proposed to overcome these limitations. An epoxy midcoat layer is introduced to provide both strong noncovalent adhesion to various surfaces and covalent linkages to hydrogel layers. The 3D hydrogel layers provide homogenous, relatively low Young's modulus and dense surface coverage and therefore shows outstanding antifouling properties toward various proteins, polysaccharides, seaweeds, and oil. Moreover, this hydrogel coating degrades slowly in sea water and facilitates the release of fouling biomolecules and organisms. Considering the great antifouling and fouling release properties, convenient coating processes, and high adhesion strength, this novel paintable antifouling hydrogel coating is anticipated to be broadly applicable for marine antifouling and other relevant fields.
The effect of ultrasonic antifouling control on the growth and microbiota of farmed European sea bass (Dicentrarchus labrax)
Résumé : Biofouling is a serious threat to marine renewable energy structures and marine aquaculture operations alike. As an alternative to toxic surface coatings, ultrasonic antifouling control has been proposed as an environmentally friendly means to reduce biofouling. However, the impact of ultrasound on fish farmed in offshore structures or in marine multi-purpose platforms, combining renewable energy production and aquaculture, has not yet been assessed. Here we study the impact of ultrasound on the growth and microbiota of farmed European sea bass (Dicentrarchus labrax) under laboratory conditions. Whereas growth and survival were not reduced by ultrasound exposure, microbiological analysis using plate counts and 16S rRNA gene based metataxonomics showed a perturbation of the gill and skin microbiota, including an increase in putative pathogenic bacteria. This warrants further research into the long-term effects of ultrasonic antifouling control on the health and wellbeing of farmed fish.
20 - Marine applications
Résumé : This chapter mainly emphasizes on the recent advancement in polysaccharide-based materials development in the large variety of marine applications such as wastewater treatment, corrosion inhibitors, drag reducer, antifouling agents, and in marine polymer coatings. Owing to the intrinsic properties of polysaccharide, functionalization of chitin, chitosan with metal nanoparticles for identification of the toxic ions present in the marine water by chemical and electrochemical methods are explored. The different separation methods for the removal of toxic ions and classification of the different types of polysaccharides were discussed in detail. Strategies toward the development of anticorrosive materials by natural and synthetic polysaccharides with different formulation were screened as marine polymer coatings in detail, pointing out their salt spray resistance, ionic conductivity, and prospective applications.
Acute and chronic effects of innovative antifouling nanostructured biocides on a tropical marine microcrustacean
Résumé : This study aimed to investigate the toxicity of innovative antifouling nanostructured biocides DCOIT and silver associated to silica nanocapsules (SiNC) on the tropical microcrustacean Mysidopsis juniae. The toxicity of the tested compounds can be summarized as follows (acute tests): DCOIT > SiNC-Ag > SiNC-DCOIT > SiNC-DCOIT-Ag > SiNC > Ag; (chronic tests): SiNC-Ag > SiNC-DCOIT-Ag > DCOIT > Ag > SiNC, although it was not possible to determine the chronic toxicity of SiNC-DCOIT. In general, our data demonstrated that mysids were more sensitive than most temperate species, and it was possible to conclude that the combination SiNC-DCOIT-Ag showed less acute toxicity in comparison to the isolated active compounds, reinforcing data obtained for species from temperate environments on the potential use of nanomaterial to reduce toxicity to non-target species. However, despite representing less risk to the environment, the compound SiNC-DCOIT-Ag is still very toxic to the non-target tropical mysid.
Toward the Application of Graphene for Combating Marine Biofouling
Résumé : The discovery of graphene has brought great innovations to materials science. Since tributyltin antifouling coatings were banned worldwide in 2008, the development of green antifouling coatings has become necessary. Recently, novel graphene-related antifouling coatings have been the focus of many studies due to their enhanced mechanical strength, excellent antifouling capabilities, and environmental friendliness. This review starts by introducing the basic antifouling mechanisms of graphene nanosheets and the possible antifouling mechanisms when graphene is incorporated into coatings. Subsequently, the progress and existing problems regarding the application of graphene in the prevention of marine biofouling are discussed. Specifically, this review focuses on six graphene-related antifouling coatings, including pure graphene film, nanohybrids, foul release coatings, photocatalytic nanocomposites, desalination membranes, and materials for uranium enrichment. The fabrication, antifouling properties, working mechanisms, and future development of graphene-related antifouling coatings are highlighted. In addition, the potential environmental risk of using graphene materials in preventing marine biofouling is explained, and the basic requirements for designing an environmentally friendly graphene-related antifouling coating are discussed. Finally, the prospect of applying graphene materials for combating marine biofouling is presented. This review aims to aid in improving the design of graphene-related green antifouling coatings.
Comparative study for marine antifouling agents based on natural sarcophine product and ZnO nanomaterials
Résumé : Fouling has significant economic influences on sea transportation and other submerged surfaces. This work aims to compare between sarcophine and synthesized ZnO nanospheres as active antifouling ingredients. The two compounds were applied on unprimed steel and were immersed in the seawater of the Eastern Harbour (E.H.), Alexandria, Egypt. Seawater hydrographic parameters were measured. 1H and 13C NMR spectra were carried out to study the structural analysis of sarcophine. ZnO nanospheres were characterized through SEM, XRD, and UV-V instruments. Each of sarcophine and ZnO nanospheres was blended solely by 2% (w/w) with a designed paint formulation of two paint ingredients besides the blank. Duplicate paint formulations were applied on unprimed steel, hanged, and immersed in the E.H. on 30/12/2018. Panels’ surfaces were followed visually and by photographic inspection for fouling succession over different interval times. They lasted for 200 days. Sarcophine showed the least fouled surface by about 15% of tubeworms and barnacles than ZnO or the blank. Most fouling were around the edges of the panel. This is due to its smoother surface, besides it has higher molecular weight than ZnO nano-particles. The hydrographic parameters of the E.H. seawater were within the normal range that these paint formulations are environmentally safe.
Recent Progresses of Superhydrophobic Coatings in Different Application Fields : An Overview
Résumé : With the development of material engineering and coating industries, superhydrophobic coatings with exceptional water repellence have increasingly come into researchers’ horizons. The superhydrophobic coatings with corrosion resistance, self-cleaning, anti-fogging, drag-reduction, anti-icing properties, etc., meet the featured requirements from different application fields. In addition, endowing superhydrophobic coatings with essential performance conformities, such as transparency, UV resistance, anti-reflection, water-penetration resistance, thermal insulation, flame retardancy, etc. plays a remarkable role in broadening their application scope. Various superhydrophobic coatings were fabricated by diverse technologies resulting from the fundamental demands of different fields. Most past reviews, however, provided only limited information, and lacked detailed classification and presentation on the application of superhydrophobic coatings in different sectors. In the current review, we will highlight the recent progresses on superhydrophobic coatings in automobile, marine, aircraft, solar energy and architecture-buildings fields, and discuss the requirement of prominent functionalities and performance conformities in these vital fields. Poor durability of superhydrophobic coating remains a practical challenge that needs to be addressed through real-world application. This review serves as a good reference source and provides insight into the design and optimization of superhydrophobic coatings for different applications.
Mechanical Properties of Protective Coatings against Marine Fouling : A Review
Résumé : The accumulation of marine organisms on ship hulls, such as microorganisms, barnacles, and seaweeds, represents a global problem for maritime industries, with both economic and environmental costs. The use of biocide-containing paints poses a serious threat to marine ecosystems, affecting both target and non-target organisms driving science and technology towards non-biocidal solutions based on physico-chemical and materials properties of coatings. The review reports recent development of hydrophobic protective coatings in terms of mechanical properties, correlated with the wet ability features. The attention is focused mainly on coatings based on siloxane and epoxy resin due to the wide application fields of such systems in the marine industry. Polyurethane and other systems have been considered as well. These coatings for anti-fouling applications needs to be both long-term mechanically stable, perfectly adherent with the metallic/composite substrate, and capable to detach/destroy the fouling organism. Prospects should focus on developing even “greener” antifouling coatings solutions. These coatings should also be readily addressable to industrial scale-up for large-scale product distribution, possibly at a reasonable cost.
Developing New Marine Antifouling Surfaces : Learning from Single-Strain Laboratory Tests
Résumé : The development of antifouling (AF) technology for marine environments is an area of intense research given the severe economic and ecological effects of marine biofouling. Preliminary data from in vitro assays is frequently used to screen the performance of AF coatings. It is intuitive that microbial composition plays a major role in surface colonization. The rationale behind this study is to investigate whether using a mixed population for the in vitro tests yields substantially different results than using single strains during initial screening. A polymeric coating was tested against single- and dual-species cultures of two common microfouler organisms for 49 days. A bacterium (Pseudoaltermonas tunicata) and a cyanobacterium (Cyanobium sp. LEGE 10375) were used in this study. Linear regression analysis revealed that Cyanobium sp. biofilms were significantly associated with a higher number of cells, wet weight, thickness, and biovolume compared to dual-species biofilms. P. tunicata alone had a biofilm growth kinetics similar to dual-species biofilms, although the P. tunicata–Cyanobium sp. mixture developed less dense and thinner biofilms compared to both single-species biofilms. Cyanobium sp. LEGE 10375 biofilms provided the worst-case scenario, i.e., the conditions that caused higher biofilm amounts on the surface material under test. Therefore, it is likely that assessing the AF performance of new coatings using the most stringent conditions may yield more robust results than using a mixed population, as competition between microfouler organisms may reduce the biofilm formation capacity of the consortium.
Antifouling Strategies for Sensors Used in Water Monitoring : Review and Future Perspectives
Résumé : Water monitoring sensors in industrial, municipal and environmental monitoring are advancing our understanding of science, aid developments in process automatization and control and support real-time decisions in emergency situations. Sensors are becoming smaller, smarter, increasingly specialized and diversified and cheaper. Advanced deployment platforms now exist to support various monitoring needs together with state-of-the-art power and communication capabilities. For a large percentage of submersed instrumentation, biofouling is the single biggest factor affecting the operation, maintenance and data quality. This increases the cost of ownership to the extent that it is prohibitive to maintain operational sensor networks and infrastructures. In this context, the paper provides a brief overview of biofouling, including the development and properties of biofilms. The state-of-the-art established and emerging antifouling strategies are reviewed and discussed. A summary of the currently implemented solutions in commercially available sensors is provided and current trends are discussed. Finally, the limitations of the currently used solutions are reviewed, and future research and development directions are highlighted.
A review on methods used to reduce drag of the ship hulls to improve hydrodynamic characteristics
Résumé : The most severe component is the frictional resistance in hydrodynamic design of the vessel. Pressure resistance can be decreased by modifying the shape of the vessel with integration of modern and more sophisticated hull forms. Since hull form optimisation is not cost effective method and sometimes impossible for decreasing drag in existing ships. Ships use large quantities of fuel to provide the necessary propulsive power and to overcome resistance in their motion across ocean surfaces. In this paper the various techniques used in the maritime industry to reduce the resistance on the hull of a ship along with their advantages and disadvantages have been discussed. On the basis of results from various reviewed research the combination of hull form optimisation method and air lubrication through injection and antifouling coating is highly recommended to decrease the total resistance on the vessel.
Mechanical Properties of Protective Coatings against Marine Fouling : A Review
Résumé : The accumulation of marine organisms on ship hulls, such as microorganisms, barnacles, and seaweeds, represents a global problem for maritime industries, with both economic and environmental costs. The use of biocide-containing paints poses a serious threat to marine ecosystems, affecting both target and non-target organisms driving science and technology towards non-biocidal solutions based on physico-chemical and materials properties of coatings. The review reports recent development of hydrophobic protective coatings in terms of mechanical properties, correlated with the wet ability features. The attention is focused mainly on coatings based on siloxane and epoxy resin due to the wide application fields of such systems in the marine industry. Polyurethane and other systems have been considered as well. These coatings for anti-fouling applications needs to be both long-term mechanically stable, perfectly adherent with the metallic/composite substrate, and capable to detach/destroy the fouling organism. Prospects should focus on developing even "greener" antifouling coatings solutions. These coatings should also be readily addressable to industrial scale-up for large-scale product distribution, possibly at a reasonable cost.
Marine natural products as antifouling molecules – a mini-review (2014–2020)
Résumé : In the present review, 182 antifouling (AF) natural products from marine microorganisms, algae and marine invertebrates reported from August 2014 to May 2020 are presented. Amongst these compounds, over half were isolated from marine-derived microorganisms, including 70 compounds from fungi and 31 compounds from bacteria. The structure–relationship of some of these compounds is also briefly discussed. Based on the work reported, a general workflow was drafted to refine the procedures for the commercialization of any novel AF compounds. Finally, butenolide, which is considered a potential environmentally friendly antifoulant, is used as a case study to show the procedures involved in AF compound work from the aspect of discovery, structure optimization, toxicity, stability, AF mechanism and coating incorporation, which highlight the current challenges and future perspectives in AF compound research.
Biofouling monitoring
Résumé : The biofouling prevention methods is a new research area. This paper presents a study of biofilm evolution (microbiota) on different surfaces, monitoring different parameters. For this research, the tests are achieved on samples as naval steel painted with different antifouling paints, and liquid wood samples introduced into the dynamic marine water system. The main parameters observed during the test are water temperature and flow. The microfouling samples are observed under the epifluorescence microscopy and quantification of biofilm using specific software. Using MATLAB software, we develop the prediction methods for biofouling prevention using the environmental parameter. The test system use the two boxes placed on the different higher, using an acquisition card the sensors data is sent to the computer for analysis.
Influence of concrete properties on the initial biological colonisation of marine artificial structures
Résumé : Artificial marine infrastructures now cover large stretches of the available natural shoreline in many parts of the world. This is having a substantial impact on the local marine ecosystems as biodiverse natural hard substrata are being replaced with man-made structures, which have been shown to support lower levels of biodiversity. The ecological value of artificial coastal structures could be enhanced through careful design of pre-fabricated ecologically engineered units. Material selection is a critical parameter in the design of these units. To maximise the potential of concrete units to support and increase biodiversity, this paper explores the impact of binder composition, aggregate type and plasticizer on surface chemistry and early biofilm formation which influence subsequent colonisation. Experiments in the current study have shown that the addition of ground granulated blast-furnace slag (GGBS) to the mix can increase the levels of biodiversity supported while maintaining engineering performance requirements in terms of strength, chloride resistance and alkalinity. Conversely the aggregate type and use of a plasticizer have a minor influence. In particular, the addition of GGBS was shown to increase the biomass of diatoms, cyanobacteria and green algae and barnacle abundance one month after immersion on both sheltered surfaces and those exposed to wave action. Results suggest that concrete composition can alter the surface chemistry of artificial structures and thereby can improve the ecological value of these structures as habitats for marine life.
Self-healing, Highly Elastic and Amphiphilic Silicone-based Polyurethane for Antifouling Coatings
Résumé : Silicone elastomer coatings have attracted increasing attention owing to its eco-friendly nature, excellent fouling release ability and drag-reducing property. However, the poor mechanical properties and lack of fouling resistance limits their applications. Herein, a silicone-based polyurethane with 2-ureido-4[1H]-pyrimidinone (UPy) and amphiphilic pendant chains is reported. The UPy groups and urethane can form hydrogen bonds with various substrates so that the coating has significantly improved adhesion strength (0.9–3.0 MPa) compared with PDMS elastomer (0.3–0.4 MPa). Moreover, the quadruple hydrogen bonding between UPy moieties allows the polymer to have excellent self-healing performance and high elasticity. The modified polymeric coating has low surface energy (24 mJ•m−2) and low elastic modulus (1.9 MPa), so it exhibits good fouling release performance. Besides, the amphiphilic side chains can effectively resist the protein adsorption and the adhesion of the marine bacteria Pseudomonas sp. and diatom Navicula incerta. The novel design can improve the resistances of silicone coating to biofouling and mechanical forces and is promising to be high-performance antifouling coatings.
Fabrication and synergistic antibacterial and antifouling effect of an organic/inorganic hybrid coating embedded with nanocomposite Ag@TA-SiO2 particles
Résumé : The combination of antifouling and biocidal methods is an efficient antimicrobial strategy to alleviate environmental biofouling. Herein, a functional organic/inorganic hybrid coating with integrated terpolymer and hybrid Ag@TA-SiO2 nano spheres was designed and fabricated for antifouling purpose for the first time. The silicon-containing terpolymer (GHM) was fabricated via a simplified free radical co-polymerization process with glycidyl methacrylate (GMA), 2-hydroxyethyl methacrylate (HEMA) and 3-(methacryloxypropyl) trimethoxysilane (MPS). It was expected that the (3-aminopropyl) triethoxysilane (KH550) would become immobilized at the epoxide ring of the GMA and eventually crosslinked, acting as a backbone for the final polymeric coating (PGHMK). Meanwhile, Ag nano-particles were decorated with tannic acid (TA) to have a composite surface structure and loaded with silica (SiO2) to form raspberries. The fabrication of the decorated and loaded antibacterial nano particle Ag@TA-SiO2 was environmental-friendly, high efficiency and low-cost. The PGHMK coating was expected to act as an effective antifouling barrier, and the embedded Ag@TA-SiO2 as a functional biocide carrier to collectively inhibit biofouling. To ensure the designed fabrication processes and the products, the microstructural, compositional, morphological changes of the copolymers and nanoparticles were characterized by means of FT-IR, 1H nuclear magnetic resonance, X-ray photoelectron spectroscopy and atomic force microscopy. The antifouling and bactericidal properties of the composite coatings were also systematically evaluated through measuring the adsorption of protein, growth of bacteria and attachment of microalgae on the coating surface. The results indicated that the coating suppressed 98.6 % of protein adsorption, and its antibacterial efficiency reached 99.1 % and 82.7 % for E. coli and S. aureus, respectively. The coating could also remarkably reduce the attachment of microalgae N. Closterium and Dicrateria zhanjiangensis by 93.5 % and 97.6 %, respectively. It is envisioned that the composite coating may provide a promising antifouling and antibacterial surface for marine engineering structures.
Enriched antibacterial and antifouling performance of organoclay filled hybrid epoxy composites
Résumé : Organically changed montmorillonite (OMMT) can significantly enhance the surface property of composite blends. In this present work, for the first time we have reported the enhanced antifouling performance on the substrate, combined with cured epoxy (CE), unsaturated polyester (UP), and organically changed montmorillonite (OMMT) blends. The newly developed CE-UP-OMMT materials were submerged into the real time marine environment with the other samples of glass, plastic, fibre (broadly used in the ship hull), and wood. Since the contact angle is increased, the surface energy is decreased to the epoxy toughened blend incorporated with clay and thus showing enhanced antibacterial and antifouling properties. It provides promising results in 1 and 3 wt% clay incorporated epoxy with 10 wt% UP composite blends which improved antibacterial and antifouling performance during the microbial and macro-fouling activity in the real-time marine environment for around three months. In the future, these blends could be new opportunities for the marine industry.
Electrochemical characteristics of antifouling coated steel structure submerged in Florida natural waters to mitigate micro- and macrofouling
Résumé : Recent findings in a Florida bridge indicated that there are synergistic effects of surface fouling to facilitate biocorrosion. Coatings that have anti-microbial, anti-fouling and barrier-characteristics are applied to steel elements in natural waters to mitigate degradation including corrosion and marine fouling. Electrochemical impedance spectroscopy (EIS) was utilized to identify the performance of a commercially-available anti-fouling coating exposed in three test sites for ~200 days. The results showed that complete prevention of fouling was not attained. EIS showed impedance dispersion associated with surface heterogeneities indicating the coating degradation and biofilm formation as result of reduced coating biocide efficacy.
Using encrusting bryozoan adhesion to evaluate the efficacy of fouling-release marine coatings
Résumé : Biofouling communities are spatiotemporally diverse, underscoring the need to assess fouling-release (FR) coating performance against common biofouling taxa at multiple field sites. Adhesion strength assessments of FR coatings incorporate few taxa into standardized protocols. This study tested the feasibility of incorporating existing ASTM barnacle protocols on tubeworms and encrusting bryozoans (EB). Additionally, trends in adhesion strength among these taxa were compared at two field sites. EB adhesion at both field sites showed consistent results and adhesion strength followed the same trend: tubeworms > barnacles >EB. Testing EB adhesion was feasible and enhanced assessments of FR coatings by increasing the diversity of assessed taxa.
Cyclic Copper Uptake and Release from Natural Seawater—A Fully Sustainable Antifouling Technique to Prevent Marine Growth
Résumé : Unwanted growth of fouling organisms on underwater surfaces is an omnipresent challenge for the marine industry, costing billions of dollars every year in the transportation sector alone. Copper, the most widely used biocide in antifouling paints, is at the brink of a total ban in being used in antifouling coatings, as it has become an existential threat to nontargeted species due to anthropogenic copper inputs into protected waters. In the current study, using a porous and cross-linked poly(ethylene imine) structure under marine and fouling environments, available copper from natural seawater was absorbed and electrochemically released back as a potent biocide at 1.3 V vs Ag|AgCl, reducing marine growth by 94% compared to the control electrode (coupon) at 0 V. The coating can also function as an electrochemical copper sensor enabling real-time monitoring of the electrochemical uptake and release of copper ions from natural seawater. This allows tailoring of the electrochemical program to the changing marine environments, i.e., when the vessels move from high-copper-contaminated waters to coastal regions with low concentrations of copper.
UNDERSTANDING NATURAL BIOFILM DEVELOPMENT ON STEEL IN MARINE ENVIRONMENTS – A REVIEW
Résumé : Surface colonisation by microorganisms is a ubiquitous process in the marine environment. The formation of a mature biofilm structure, which is described as an aggregate of attached cells surrounded by extracellular polymeric substances (EPS) is the final stage of colonisation. In this form, bacteria, fungi and archaea have been implicated in several deleterious effects on substrate surfaces; for example biofouling and subsequent microbiologically influenced corrosion (MIC). Although it is well documented that marine biofilms form on almost any submerged artificial or natural surface, there are still no truly effective and environmentally friendly treatment or prevention options available. Part of the reason biofilm growth and establishment cannot be adequately controlled is the lack of fundamental understanding of natural multi-species biofilm development. Polymicrobial systems give rise to complex synergistic and competitive behaviour, which is overlooked in single-species in vitro studies. So far, single-species studies have provided a great deal of information on how microorganisms assemble simple biofilms. Conversely, multi-species studies have been limited up until recently due to technique and data processing restrictions. Today, with access to advanced microscopic and molecular techniques, among others, there is greater potential for multi-species studies. It is important for the applicability of research conclusions now to move away from single-species investigations and into studies incorporating a variety of isolates which reflect marine heterogeneity. The purpose of this review is to compile the current literature and knowledge gaps surrounding multispecies biofilms, with particular focus on the development process in marine conditions on steels.
Diversity of periphytic ciliates on vessel surface and effects of antifouling paint from the surface
Résumé : Periphyton on vessel surface has a potential risk on endemic ecosystems through moving habitats on transportation routes. As ciliates can live on various natural and artificial substrates, they were targeted to investigate vessel biofouling organisms in this study. To know diversity of periphytic ciliates, biofilms were sampled from the surface of five vessels, and then ciliate species in the samples were identified by molecular analyses as well as microscopic observations of living and silverimpregnated cells. To monitor effects of antifouling biocidal agents painted on the vessel surface, non-treated and antifouling coated (Intersmooth 7475 Si) plates were deployed in a nearshore water for 7 weeks, and then ciliate species succession on the plates was weekly tracked. A periphytic ciliate species, Diophrys appendiculata, was isolated from the plates and cultured to be established as a toxicity test species for antifouling biocide Sea-Nine 211. Fourteen species of periphytic ciliates were found from the samples of vessel surface. Ciliate fauna was different on the non-treated and antifouling coated plates for earlier 4 weeks. Aspidisca leptaspis and D. appendiculata were attached on the non-treated plates while Euplotes balteatus on the paint treated plates. D. appendiculata exhibited toxic responses to Sea-nine 211 as follows; very low mortality at 1-250 ppb concentration range, encystment of ciliate cells at 500-1000 ppb range, and 100% mortality within 5 minutes at 10,000 ppb. Future studies need to address in detail survival and invasive strategies of periphytic ciliates on vessel surface.
ANALYTICAL METHODS FOR ANTIFOULING BOOSTER BIOCIDES DETERMINATION IN ENVIRONMENTAL MATRICES : A REVIEW
Résumé : Since the discovery of their toxicity to aquatic environments, antifouling booster biocides (ABBs) have been widely researched and detected at trace levels in diverse environmental compartments including water, sediment, and, less frequently, biota. Hence, the reliable assessment of environmental risks posed by ABBs requires the development of analytical methods sufficiently robust, accurate, and precise for the simultaneous trace-level determination of ABBs. Herein, we summarize outstanding sample preparation procedures for the analysis of main ABBs in environmental matrices, describing techniques ranging from traditional extraction methods to novel miniaturized and micro-extraction ones, which have recently received much attention due to their reduced number of steps, low operational cost, and greater respect for the environment. The main applied chromatographic-based methods coupled to different detection techniques are also addressed. Despite the recent development of numerous ABBs determination methods, this topic continues to draw attention because of the lack of standardization among methods, despite legislation set up maximum standards levels for selected ABBs, and the need to monitor ABB transformation products for a reliable ecological risk assessment.
Challenges of coatings in aerospace, automobile and marine industries
Résumé : Coatings are multifaceted having raw materials combined and utilized to a prepared substrate by allowing it to be dried and cured to obtain effectiveness. Majority of coating challenges occurs in coating manufacturing and its application in different environment not shielded away from the impact of rain, sunlight, wind, heat, cold, humidity, and oxygen. Few coatings, including those applied in marine, aerospace, automobile and medical cannot resist some difficulties arising from corrosion. This paper focuses on identifying the challenges in marine, aerospace and automobile. In marine, the antifouling coating at the watertight body of the ship destroy organisms before they get close to it. Tributyltin (TBT), which is released to the ocean or the sea happens to be the most effective compound used for antifouling coating but its pose serious problems to marine organism due to its toxic substance .In automobile, application of chromium coating is the main source of exposure for workers leading to sneezing, headache, skin irritation, ulcers and respiratory disorder because of its ions that comes in contact with the environment in form of chromate and dichromate anions from the sewage while in aerospace ,movements of a aircraft structural joint would deform, elongate the coating system making the structural component of the aircraft coating system a major challenge in determining aircraft joint displacement. The essence of identifying coatings challenges is to find measure of ensuring substrate are improve in terms of ;appearance, bonding, moisture ability, resistance to wear etc. Hard chromium coated constituents can now find application in agricultural equipment’s, aircraft industry, automobile, marine and other industries.
Fabrication of Bio-based Amphiphilic Hydrogel Coating with Excellent Antifouling and Mechanical Properties
Résumé : Antifouling coatings are crucial to protect marine facilities and aquacultures from the damage of microorganisms for long-term serves. However, it is still a challenge to fabricate coating with excellent antifouling performance and superior mechanical stability. Here, we report a bio-based amphiphilic hydrogel coating with excellent antifouling and mechanical properties. The coating was achieved by the in-situ formation of hydrophobic and hydrophilic interpenetrating polymer network (IPN). The hydrophobic part from a synthesized silicon-containing epoxy resin contributes to superior mechanical properties including high tensile strength and excellent adhesion of 5B. While the hydrophilic hydrogel part from the cross-linking of a hydrophilic polymer with AgNPs gives excellent antifouling properties, resist to proteins, bacteria, algae, and other marine organisms. The antifouling performance of the coating was evaluated by the attachment of proteins (BSA-FITC), bacteria (Escherichia coli and Bacillus subtilis), and Algae (Navicula torguatum and Phaeodactylum tricornutum). The results show that the bio-based amphiphilic hydrogel coating (e.g. SA-1-5) endows surface with excellent resistance to the fouling of proteins, bacteria and microorganisms. The overall antifouling and mechanical properties of the amphiphilic coating was also evaluated by field test in East China Sea from June 3rd 2020 to July 17th 2020 that the bio-based amphiphilic hydrogel coating was intact and almost no marine organisms attached. This work provides a new strategy for the fabrication of bio-based and high-performance antifouling coatings.
Hydrodynamics and surface properties influence biofilm proliferation
Résumé : A biofilm is an interface-associated colloidal dispersion of bacterial cells and excreted polymers in which the microorganisms find protection from the environment. Successful colonization of a surface by a bacterial community typically means a detriment to human health or property. Insight into the biofilm life-cycle provides clues on how their proliferation can be suppressed. In this review we follow a cell through the cycle of attachment, growth, and departure from the colony. Among the abundance of factors that guide the three phases, we focus on hydrodynamics and stratum properties due to the synergistic effect they have on bacteria rejection and removal. Cell motion, regardless if facilitated by the environment via medium flow or self-actuated by use of an appendage, drastically improves the survivability of a bacterium. The growth of the colony is similarly guided by mainstream flow and the convective transport throughout the biofilm. Even after growth, hydrodynamic traction forces on a biofilm can elicit strongly non-linear viscoelastic responses from the biofilm soft matter. As the colony exhausts the means of survival at a location, a set of trigger signals activates mechanisms of bacterial release, also facilitated by fluid flow. Once in the vicinity of a stratum, a single cell is exposed to near-surface interactions, such as Van der Waals, electrostatic and specific interactions, similarly to any other colloidal particle. The success of the attachment and the potential for detachment is heavily influenced by surface properties such as the material type and topography. A review of the hydrodynamics and the surface properties provides insight into future research avenues.
Antifouling Surfaces Enabled by Surface Grafting of Highly Hydrophilic Sulfoxide Polymer Brushes
Résumé : Antifouling surfaces are important in a broad range of applications. An effective approach to antifouling surfaces is to covalently attach antifouling polymer brushes. This work reports the synthesis of a new class of antifouling polymer brushes based on highly hydrophilic sulfoxide polymers by surface-initiated photoinduced electron/energy transfer-reversible addition-fragmentation chain transfer (PET-RAFT) polymerization. The sulfoxide polymer brushes are able to effectively reduce nonspecific adsorption of proteins and cells, demonstrating remarkable antifouling properties. Given the outstanding antifouling behavior of the sulfoxide polymers and versatility of surface-initiated PET-RAFT technology, this work presents a useful and general approach to engineering various material surfaces with antifouling properties, for potential biomedical applications in areas such as tissue engineering, medical implants, and regenerative medicine.
Photocatalytic antifouling coating based on carbon nitride with dynamic acrylate boron fluorinated polymers
Résumé : Based on the situation of marine biofouling and the ecological crisis caused by toxic antifouling paints, a series of environmental carbon nitride (C3N4) nanocomposite films (CNPs) were prepared by incorporating C3N4 into a self-polishing acrylate boron fluorinated polymer (ABFP). The antifouling performance was evaluated by the diatom antisettling test, photocatalytic antibacterial measurements and a mussel settlement assay. The results showed that the optimal content of C3N4 to inhibit the adhesion of diatoms was 3-7 wt%, and the antibacterial rate of Staphylococcus aureus (S. aureus) and Escherichia coli (E. coli) reached 98.10% and 96.94% in the presence of 7 wt% C3N4 under irradiation with visible light for 90 min. In addition, the CNPs and ABFP showed to an ability to expel mussels. As a synergistic effect, the self-renewable polymer surfaces could also strip the attached fouling organisms without light. The undifferentiated growth rates between the CNPs and blank proved the environmental properties of the prepared films. The chemical oxygen demand (COD) values showed that the addition of C3N4 contributed to the eco-friendly properties of the CNPs.