Corrosion occurs when iron reacts with the oxygen in the air, or even better, with the oxygen in water that sits on it. Rust happens naturally without any real help from us. Iron is a very common material for making strong objects, and steel is made mostly of iron. Most kinds of steel will rust. This can be counteracted by the use of corrosion inhibitors. What we can do, is trying to keep metal dry so that the water doesn't accelerate the rusting process; we can also purchase things that are made from metals that are designed not to rust (eg. stainless steel).

There are materials that provide protection against rust in most hardware stores. These work by adding an extra coat of a material over the iron so that the oxygen cannot get in.