Metal corrosion

Look at the different metal articles used at home. As many of them get older, the metal loses its shine, its surface becomes rough and its colour changes.

Think of a time when you found that a bucket, a pan or some other article left unused in a corner of the house had worn through with holes after some time. Those articles were made of iron or steel. The corrosion of iron or steel exposed to the air is called, in particular, rusting.

Why rusting costs so much

Iron is the metal people use most, so it is also the metal produced most in the world. A great deal of the iron made is used to make steel, and iron and steel go into vehicles, ships, bridges, machine parts and countless other products. So rusting is an economically harmful process: every year a large share of the world's iron is lost to it, and rusted bridges, pipes and ship hulls have to be repaired or replaced. That is why this section asks what rusting needs, and how to stop it.

What kind of process happens when iron rusts? Why does an iron tool left in the garden rust more easily than one kept indoors? The activities on the next pages look into these questions one factor at a time.