Corrosion or degradation involves deterioration of material when exposed to an environment resulting in the loss of that material, the most common case being the corrosion of metals and steel by water. The changes brought about by corrosion include weight loss or gain, material loss, or changes in physical and mechanical properties.

Metal corrosion involves oxidation-reduction reactions in which the metal is lost by dissolution at the anode (oxidation). The electrons travel to the cathode where the reduction takes place, while s move through a conducting solution or electrolyte. A positive and a negative pole, called the cathode and the anode respectively, are thereby created with a current flow between them. Thus the process of corrosion is basically electrochemical.

For corrosion to occur, certain conditions must be present. These are: (1) a potential difference between the cathode and the anode to drive the...