Corrosion is defined as the degradation of a material by a chemical or electrochemical reaction with the surrounding environment. Metal corrosion is normally tbe result of an electrochemical reaction taking place on the surface, which converts the metal into oxides or other corrosion products. The corrosion product of iron and steel is the rust, which is porous and loosely adherent to the surface of the metal. It offers little or no protection from further corrosion.