Question

Explain why tin protects copper more efficiently as compared to iron?

Answer 1

1. Tin protects copper more efficiently than iron because the standard reduction potential (SRP) of tin Sn²⁺/Sn is −0.14 V, which is lower than that of copper Cu²⁺/Cu = +0.34 V.
2. This means tin has a much greater tendency to get oxidised than copper. Therefore, if the tin coating on copper gets scratched or develops cracks, tin undergoes oxidation in preference to copper, thus protecting it.
3. In contrast, the SRP of iron Fe²⁺/Fe = −0.44 V is lower than that of tin. This means iron is more easily oxidised than tin.
4. So, if the tin coating on iron gets damaged, the exposed iron acts as the anode and oxidises faster, leading to rapid rusting. Therefore, while tin can sacrificially protect copper, it cannot do the same for iron.