Physical barrier

One way to protect an iron or steel object is therefore to cover its surface with a physical barrier. Paint, oil or a plastic coating can stop oxygen and water reaching the metal. This works only while the barrier remains intact: a scratch may expose the iron beneath it, allowing rusting to begin there.

A physical barrier separates the metal from its surroundings. Paint, grease, oil and plastic coatings can all stop oxygen and water reaching an iron or steel surface. Different barriers suit different products: grease or oil can cover moving parts, while paint or plastic can provide a longer-lasting outer coating.