. . Prevention of Corrosion The rusting of iron can be prevented by painting, oiling, greasing, galvanising, chrome plating, anodising or making alloys. Galvanisation is a method of protecting steel and iron from rusting by coating them with a thin layer of zinc.
The galvanised article is protected against rusting even if the zinc coating is broken. Can you reason this out? Alloying is a very good method of improving the properties of a metal. We can get the desired properties by this method.
For example, iron is the most widely used metal. But it is never used in its pure state. This is because pure iron is very soft and stretches easily when hot. But, if it is mixed with a small amount of carbon (about .
%), it becomes hard and strong. When iron is mixed with nickel and chromium, we get stainless steel, which is hard and does not rust. Thus, if iron is mixed with some other substance, its properties change. In fact, the properties of any metal can be changed if it is mixed with some other substance.
The substance added may be a metal or a non-metal. An alloy is a homogeneous mixture of two or more metals, or a metal and a non- metal. It is prepared by first melting the primary metal, and then, dissolving the other elements in it in definite proportions. It is then cooled to room temperature.
Iron pillar at Delhi The wonder of ancient Indian metallurgy The iron pillar near the Qutub Minar in Delhi was built more than years ago by the iron workers of India. They had developed a process which prevented iron from rusting. For its quality of rust resistance it has been examined by scientists from all parts of the world. The iron pillar is m high and weighs tonnes ( kg).