A red, orange, or yellowish-brown substance which forms progressively as a flaking, permeable coating on the surface of iron and its alloys as a…

The process of becoming or fact of being rusty (rusty, adj.1 1); an instance of this. Also concrete: a flake or piece of rust (rare).

? Rust, oxide.

A corroded surface on metal; esp. verdigris on copper. Cf. canker, n. 2. Also figurative.

The patina that copper and brass acquire with age; verdigris. Occasionally more widely: an analogous coating on any metal.

A white coating or discoloration produced on the surface of various metals by exposure to moist air or other corrosive agents; esp. (in early use)…

Surface oxidation, rusting.