Potassium Oxalate Inhibits Corrosion of Mild Steel by Ferric Ion

Potassium oxalate inhibits the corrosion of AISI 1010 steel in 2.5 pH H2SO4 solutions with and without Fe3+ ion at inhibitor efficiencies up to 98%. Ferric ion exerts a synergistic influence with oxalate ion. The minimum oxalate concentration required is directly proportional to the ferric ion concentration in solution. Inhibition is caused by 30.5 to 116.8 μ thick ferrous oxalate film, i.e., ß-FeC2O4·2H2O, identified by X-ray diffraction analysis. Based on potential-time and current density-time curves, a three-stage mechanism for inhibition is postulated. Possible applications of this inhibitor in the mineral industry are suggested.