There are many different variants of corrosion, reflecting both the impact of different environments and the failure mechanism. Corrosion is the gradual destruction of materials, usually metals, by chemical or electrochemical reaction with their environment. As such, the refined metal i.e. steel returns back to a more stable form i.e. an oxide, which in the case of steel is an iron oxide (rust).
For non-corrosion resistant materials, general corrosion is the most common form of corrosion.
For more corrosion-resistant materials, localised corrosion is the most common form of corrosion.
Very specific forms of corrosion include HICC (hydrogen-induced corrosion cracking), MIC (microbiologically-induced corrosion), SCC (stress corrosion cracking), and intergranular corrosion. For this reason, a whole specialism has developed around the identification, control and prevent of corrosion mechanisms.