Why does aluminium not corrode right through? (b) What is meant by 'anodising' ? Why is it done?

Aluminium is more reactive than iron and it forms a oxide layer when come in contact with air that is why aluminium do not corrode

(b) Anodising is the process of thickening of aluminium oxide layer on the surface of aluminium objects by electrolysis. It is done to provide more protection to the aluminium object from corrosion.