Question

Aluminium is more reactive than Iron and yet there is less corrosion of Aluminium when both are exposed to air under similar conditions, explain.

Answer 1

Aluminium is more reactive than Iron but is less corrosive when exposed to air:

• Aluminium forms a natural layer of Aluminium oxide when exposed to air.
• This layer prevents the underneath metals to come in contact with air.

$$\begin{gathered} 2\mathrm{Al}+3{\mathrm{H}}_2\mathrm{O}\to {\mathrm{Al}}_2{\mathrm{O}}_3+3{\mathrm{H}}_2 \\ \mathrm{Aluminium}\mathrm{Water}\to \mathrm{Aluminium}\mathrm{oxide}\mathrm{Hydrogen} \end{gathered}$$

• Unlike Iron, where the whole metal is exposed to moist air forming rust and there is no protective layer.
• The rust usually flakes off over time exposing the Iron underneath the metal to air which doesn’t happen in the case of Aluminium.

Aluminium is reactive and yet less corrosive is because of a protective layer of Aluminium oxide which prevents further corrosion