Corrosion electrochemistry of metallic iron in reduced ilmenite with ammonium chloride solution

Abstract

Separation of iron and titanium by reduction-corrosion method from ilmenite had the advantages of less pollution, simple process, and low cost compared with other methods. To identify the determinants for corrosion reaction of reduced ilmenite, the corrosion electrochemistry of metallic iron in ammonium chloride solution was carried out. The metallic iron was oxidized to form dense Fe2O3 and Fe3O4 in NH4Cl solution at pH of 3.60, resulting in the passivation of metallic iron electrode surface. However, the anode passivation film was destroyed by the chloride ions in the NH4Cl solution, which promoted the corrosion reactions of metallic iron. The corrosion of metallic iron in the 1.60 wt.% NH4Cl solution was controlled by the cathode reaction with a control degree of 95.86%. Decreasing the cathodic polarization could improve the corrosion rate of metallic iron. The decrease of pH value in electrolyte promoted the anode reaction of metallic iron in the NH4Cl solution and reduced the passivation of metallic iron. The Ca2+ and Mg2+ ions in electrolyte increased the difficulty of the metallic iron corrosion reaction. The Fe(OH)3 accumulated in electrolyte slowed down the corrosion reaction rate of metallic iron.