It is the destruction of a material caused by a chemical, or electrochemical reaction with its environment. The material and its environment form an element of the corrosion which is influenced by the electrical potential of the metallic materials, and also by the differences in temperature and concentration.

All metals have a tendency to return to the stable condition in which they are found in nature, that is to say, thermodynamically speaking, a stable state.

This tendency is much stronger in the less stable metals, which means that they can be classified in accordance to their stability in order of decreasing activity and increasing potential.