The study of cathodic protection potentials of selected electroactive anions on galvanized steel in acidic medium by weightloss and hydrogen evolution techniques

The cathode protection potentials of selected electroactive anions, namely: OH ⁻,I ⁻, Br ⁻, Cl ⁻, NO₃⁻, MnO₄⁻, F ⁻ on the corrosion of mild steel in tetra-oxo-sulphate (vi) acid, (H₂SO₄) have been studied. Weight loss and hydrogen evolution measurements reveal that hydroxide ion (OH⁻) exhibits a higher maximum cathode protection efficiency than the rest of the anions studied. Generally, cathode protection was found to increase with increase in anion concentration and temperature. Electro-nation of the cathode sites as well as chemisorptions have been proposed for the anions. The difference in the cathode protection efficiency of the anions has been explained in terms of the solubility of their potassium salts as well as the strength of anion – metal bond.