(1) The electrochemical degradation of metals or alloys caused by reaction with their environment, which is accelerated by the presence of acids or bases. In general, the corrodability of a metal or alloy depends on its position in the activity series. Corrosion products often take the form of metallic oxides. This is actually beneficial in the case of aluminum and stainless steel, because the oxide forms a strongly adherent coating that effectively prevents further degradation. Hence, these metals are widely used for structural purposes. The rusting of iron is a familiar example of corrosion that is catalyzed by moisture. Acidic soils are highly corrosive. Sulfur is a corrosive agent in automotive fuels and in the atmosphere (as SO2). Sodium chloride in the air at locations near the sea is also strongly corrosive, especially at temperatures above 21C. Copper, nickel, chromium, and zinc are among the more corrosion-resistant metals and are widely used as protective coatings for other metals. Excellent corrosion-resistant alloys are stainless steel (18 Ni–8 Cr), Monel metal (66 Ni–34 Cu), and duralumin.(2) The destruction of body tissues by strong acids and bases. See Corrosive Material; Protective Coating; Paint; Tarnish.
