Iron, as well as iron alloys, rusts because of a chemical reaction known as oxidation. When iron is exposed to moisture or oxygen, oxidation occurs. During this chemical reaction, iron is converted into iron oxide. The iron oxide typically has a reddish, flaky appearance that becomes progressively worse over time.

What happens when metal rusts?

Rusting is an oxidation reaction. The iron reacts with water and oxygen to form hydrated iron(III) oxide, which we see as rust.

What is it called when metal rusts?

Rust, commonly referred to as oxidation, occurs when iron or metal alloys that contain iron, such as steel, are exposed to oxygen and water for a long period of time. Rust forms when iron undergoes the process of oxidation but not all oxidation forms rust.