How is corrosion an example of a redox reaction?

Corrosion is a classic example of a redox reaction because it involves both oxidation and reduction occurring simultaneously.

Take the example of iron rusting (formation of Fe₂O₃·xH₂O):

1. Oxidation (loss of electrons):
   • Iron (Fe) loses electrons to form iron ions:
     • Fe → Fe²⁺ + 2e⁻
2. Reduction (gain of electrons):
   • Oxygen from air reacts with water and the electrons released by iron to form hydroxide ions:
     • O₂ + 4e⁻ + 2H₂O → 4OH⁻
3. Overall reaction:
   • The Fe²⁺ ions further react with oxygen and water to form hydrated iron(III) oxide, which we see as rust.

Why it’s a redox reaction:

• Iron is oxidized (loses electrons) → oxidation.
• Oxygen is reduced (gains electrons) → reduction.

So corrosion is not just a chemical change—it’s a continuous electron transfer process between metal and its environment, which is exactly what defines a redox reaction.