Corrosion of aluminium is useful. Corrosion of Aluminium occurs when the metal is exposed to oxygen. It undergoes protective corrosion (OR SACRIFICIAL CORROSION) to form a layer of aluminium oxide, Al3O2 .
According to the following reaction :
4 Al(s) + 3 O2(g) ? 2 Al2O3(s)
Thus, a protective layer of aluminium oxide is formed on the surface of the metal. This layer sticks firmly to the metal surface. Thus, preventing the lower layers from corrosion. Therefore it is advantageous.