ABSTRACT
All metals and alloys are subjected to corrosion when in contact with body fluid as the body environment is very aggressive owing to the presence of chloride ions and oxygen. A variety of chemical reactions occur on the surface of a surgically implanted alloy. Corrosion is an irreversible interfacial reaction of a material with its environment, resulting in the loss of the material or in the dissolving of one of the constituents of the environment into the material. The most familiar example of corrosion is the rusting of steel due to chemical transformation of iron into loose iron oxide by chemical reaction with water and oxygen. Although passive films reduce the corrosion rate of biomedical alloys, they do not entirely suppress it. Metal atoms can still be oxidised to metallic ions and diffuse through the passive film. Furthermore, passive films are thin and can be easily destroyed by scratching or rubbing against a solid counterpart, for example, in joint replacements.
