Oxidation-Reduction Reaction

Corrosion reactions also involve oxidation of substances by oxygen. However, these reactions are limited to the oxidation of metals, do not give off the light associated with combustion, and usually occur when moisture is present. Corrosion occurs most rapidly when metals are strained and bent; the metals rapidly oxidize in the strained regions. Corrosion can be inhibited by covering metal surfaces with paint or metals which are less easily oxidized. An example is the plating of iron with chromium on nickel. In some cases, more easily oxidized metals are used to coat or come in contact with the metal that is being protected. Then these will react more readily with the oxygen. An example is galvanizing: coating iron with zinc. Some substances such as aluminum quickly form an oxide coating in areas that are exposed, but this coating is inert to oxygen and this prevents further corrosion. That is why aluminum does not "rust."