Iron is one of the most used metals in our daily life, but often we see that there is corrosion on the iron surface and this corrosion happens because of rust which is composed on Iron Oxide. The compound, iron oxide, is a result of the reaction between iron and oxygen in the presence of air moisture and water. If sufficient time, oxygen and water is given, any iron mass will convert entirely to rust and disintegrate. The surface of rust is flaky and doesn’t provide any protection to the underlying iron.
Once rusting is started, the iron continues to corrode because rust is permeable to air and water. The interior metallic iron beneath the rust layer again gets in touch of air and water, and therefore, rust forms again
We abundantly use iron and steel products, and this is why prevention of rust has become a major economic activities.
• Barrier Protection: a barrier film can be introduced between the iron and atmospheric oxygen and moisture. A barrier protection can be achieved by painting the surface or by coating the surface with a very thin film of grease or oil or by electroplating iron with metal such as copper, nickel and chromium etc.
• Sacrificial Protection: in this method, iron surface is covered with a layer of more active metal such as zinc. Zn loses e in preference to iron and prevents the rusting of iron. The process by which iron is protected by Zinc is called galvanization. Zinc, aluminum and magnesium powder dissolved in paints are also effective to protect iron from rust.
• Use of Anti-rust solutions: The alkaline chromate and alkaline phosphate act as anti-rust solutions. When iron objects are dipped into strongly alkaline solution of sodium phosphate, a protective insoluble iron phosphate film is formed. The film prevent the object to be rusted.