Question

Corrosion is an electrochemical phenomenon. The oxygen in moist air reacts as follows:

\[\ce{O2(g) + 2H2O(l) + 4e^{-} -> 4OH^{-}(aq)}\]

Write down the possible reactions for corrosion of zinc occurring at anode, cathode, and overall reaction to form a white layer of zinc hydroxide.

Answer 1

Anode: \[\ce{Zn(s) -> Zn^{2+}(aq) + 2e^{-}}\]

Cathode: \[\ce{O2(g) + 2H2O(l) + 4e^{-} -> 4OH^{-}(aq)}\]

Overall: \[\ce{2Zn(s) + O2(g) + 2H2O(l) -> 2Zn^{2+} (aq) + 4OH^{-} (aq)}\]

\[\ce{2Zn(s) + O2(g) + 2H2O(l) -> 2Zn(OH)2 (ppt)}\]