Corrosion // Rusting of iron


      It is the slow process of eating away metals by the reaction of atmospheric air and moisture, e.g. rusting of iron, formation of green coating over copper etc.


     Rusting of iron is prevented by galvanising, by making alloys, painting, greasing or oiling and tin-plating and chrome plating . Explained below --

1. Galvanisation - It is the process of coating iron and steel object with a thin layer of zinc. It is done by dipping the object in molten zinc. The galvanised article is protected against rusting even if the zinc coating is broken.

2. Alloying - It is the method of improving the properties of a metal by mixing the metal with another metal or non-metal.

3. Alloying of iron - Pure iron is very soft and stretches easilywhen hot. It is mixed with a small amount of carbon and it becomes hard and strong. Iron is mixed with many metals to form different types of alloys. For example, when iron is mixed with nickel and chromium, stainless steel is obtained which is hard and does not rust.

4. Painting - Rusting of iron can be easily prevented by coating the surface with a paint which protects iron from air and moisture.

5. Greasing or Oiling - When grease or oil is applied to the surface of iron object then air and moisture cannot be come in contact with it and hence rust is prevented. Thus greasing or oiling prevent from rusting of iron.

6. Tin plating and Chromium Plating - Tin and Chromium metals are resistant to corrosion. So when a thin layer of tin metal is applied on iron object by electroplating then iron and steel objects are protected from rusting. 

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