Another word for rust

Iron rust sometimes contains magnetite.

Copper rust has the same composition as malachite; it results from the action of carbon dioxide and water on the metal.

inch of concrete to preserve them from damage by rust or fire.

As if on cue, an old car with more rust than clear metal chugged to a stop at the dollar store.

It is not brittle like porcelain and cast iron, not poisonous like lead-glazed earthenware and untinned copper, needs no enamel to chip off, does not rust and wear out like cheap tin-plate, and weighs but a fraction of other substances.