Rusting of Iron

• Rusting is an oxidation process where iron, oxygen and water react to form hydrated iron oxide.

• Both air and water are necessary for iron to rust.

1. With both air and water, iron rusts.
2. A layer of oil prevents air from entering the water. With no air, iron does not rust.
3. Calcium chloride absorbs water. With no water, iron does not rust.

Prevention of Rusting

1. Barrier Method

Rusting can be prevented by blocking water and oxygen from coming in contact with iron.

Some common methods of preventing contact with water and oxygen are:

• painting
• coating with a thin layer of plastic
• oiling and greasing

• Galvanising is adding a protective layer of zinc coating to iron. 
• Since zinc is more reactive than iron, zinc becomes oxidised first. 
• Zinc loses two electrons and forms Zn²⁺, preventing iron from losing electrons and becoming oxidised.
• Magnesium is also frequently used as a sacrificial method.

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