Answer these questions selecting the appropriate option given below:

Assertion (A) : Anodising is a method to prevent metal from corrosion.

Reason (R) : Anodising is a process of coating iron with a layer of zinc.

A is true but R is false.

The correct answer is option 3. A is true but R is false.

Anodising is a process of forming a thick oxide layer of aluminium. Aluminium develops a thin oxide layer when exposed to air. This aluminium oxide coat makes it resistant to further corrosion. The resistance can be improved further by making the oxide layer thicker. During anodising, a clean aluminium article is made the anode and is electrolysed with dilute sulphuric acid. The oxygen gas evolved at the anode reacts with aluminium to make a thicker protective oxide layer. This oxide layer can be dyed easily to give aluminium articles an attractive finish.