The corrosion can be prevented by cathodic protection. It involves application of an electric potential in opposition to the emf of the undesirable electrochemical cells formed on the surface of the metal. If the corrosion of iron involves the following reactions, the minimum electric potential to be applied for cathodic protection in V is O2(g)+4H (aq)++4e−1→2H2O(l);E0=1.23V2Fe(S)→2Fe2++2e−1;E0=−0.44V