Question

Aluminium is more reactive than iron yet there is less corrosion of aluminium as compared to iron when both are exposed to air why

Answer 1

Aluninium reacts with air to form a thin layer of Al2O3 on it. When this thin layer is formed, it provides protection for the remaining aluminium below the layer, and thus the remaining aluminium doesn't react with air. But iron reacting with moist air doesnt form any thin layer (it instead forms flakes of rust) so the iron gets corroded completely, gradually.

Answer 2

Al undergoes just corrosion . Great affinity fo o2 so al2o3 formed on the surface stops further reaction
Iron undergoes rusting removal of iron oxide formed that flakes away leaving the inner surface for further corrosion I.e rusting