During this reaction, the oxygen and water react with iron to form flakes of iron oxide hydrate on the metal surface.

Most transition elements react slowly with cold water, or not at all. Iron reacts with water and oxygen at room temperature to form hydrated iron(III) oxide, or rust.

When sodium is cut or scratched, its freshly exposed shiny surface rapidly turns dull as a thin layer of sodium oxide forms: Other metals may oxidise more slowly. Gold and other very unreactive ...