Résumé : In this chapter, principles of corrosion processes are illustrated with special emphasis on electrochemical aspects. Galvanic and electrolytic cells implicated in various corrosion and protection processes are analyzed with examples. Concentration cells are outlined with reference to galvanic corrosion and formation of differential aeration (oxygen) regions leading to pitting corrosion. Electrochemical kinetics and mixed potential theory are discussed. Active-passive transition in metals and alloys is brought out. Anodic and cathodic protection based on electrochemical principles find technological applications in industrial corrosion protection. Mechanisms involved in biofouling and microbially influenced corrosion are critically analyzed. Human body as a corrosion environment with reference to implanted biomaterials is also brought out.