The deterioration of a material by chemical or electro-chemical interaction with its environment. Corrosion can take on many forms depending on the type of material which is corroded, the stresses the material is subjected to in service while corrosion is occurring, and the environment to which the material is exposed. Examples of the various types of corrosion include uniform (general) corrosion, pitting corrosion (small concentrated corrosion), intergranular corrosion (at the microscopic crystal boundaries of a material), and selective leaching (corrosion of only one element in a multi- element alloy).