Which of them is likely to corrode till the level marked by the line FIRST? Justify your answer.

Question

Equal sized bars of aluminium and iron are exposed to the environment as shown below.

Which of them is likely to corrode till the level marked by the line FIRST? Justify your answer.

Answer 1

The iron bar will corrode till the level marked by the line first.

Iron gets oxidised on exposure to air and moisture. The layer of rust formed on the surface allows air and moisture to pass through and reach the metal, causing corrosion to continue.

Aluminium gets oxidised on exposure to air. The layer of oxide formed on the surface forms a protective coating that prevents air from reaching the metal and thus prevents further corrosion.