Gradual deterioration of a solid (especially metals) due to chemical processes such as oxidation or the action of a chemical agent. Some corrosion products, like metal patinas, can be protective; others, like rust, can be harmful. Corrosion is often accelerated by contact with materials that generate acidic vapours – e.g. wood, plastics.

Green corrosion product on a bronze bell. Photo courtesy of Alice Cannon.
White corrosion product is visible on the metal components of this pocket knife handle. Photo courtesy of Christine Ianna.

Other visual glossaries