The chemistry of corrosion of iron is essentially an electrochemical phenomenon. Explain the reactions occurring during the corrosion of iron in the atmosphere.

The impure iron surface behaves like small electrochemical cell in the presence of water containing dissolved oxygen or carbon dioxide. In this cell pure iron acts as an anode and impure iron surface acts as cathode. Moisture having dissolved CO₂ or O₂ acts as an electrolyte.

The reactions at cathode and anode are as follows:

Anode: 2Fe (s) → 2Fe²⁺ + 4e^-

Cathode: O₂(g) + 4H⁺ (aq) + 4e^-→ 2H₂O (l)

Overall Reaction: 2Fe (s) + O₂(g) + 4H⁺ (aq) → 2H₂O (l)