Question

why aluminium made metal was not corroded

Answer 1

It is because of aluminium oxide layer. Aluminium outer surface layer is oxidized whenever it came in contact with the air and so result in aluminium oxide layer which is resistive in nature and remain attached to it. So due to this it act as protective layer to inner aluminium to get oxidized with air while in iron as the surface layer of iron is oxidized, it form rust which is not remain attache.

Answer 2

Answer:

Aluminum oxide consists of atoms of aluminum and oxygen bonded together.

But Brown and Trainor discovered that, when water molecules come in contact with aluminum oxide, the aluminum and oxygen atoms on the surface move apart -- in some cases separating by more than 50 percent compared to their normal molecular positions.

As a result, when the outer layer of aluminum oxide gets hydrated or wet, its

structure changes just enough to become chemically inert and thus unable to react rapidly with additional water molecules or atmospheric oxygen. This change in molecular structure is why aluminum oxide metal resists corrosion.