Pressure leaching of reduced ilmenite: electrochemical aspects

The anodic dissolution of iron and cathodic reduction of oxygen were studied in ammonium chloride solutions over the temperature range 30–150°C and at a total pressure up to 780 kPa using the rotating disc electrode technique. Corrosion current densities determined by the Evans' diagram and linear polarisation method showed that the corrosion rate increases with increasing temperatures and oxygen partial pressures. The industrial importance of this reaction is in the production of synthetic rutile via the Becher Process which involves the high temperature reduction of ilmenite followed by the forced corrosion of metallic iron from the reduced ilmenite matrix. Results obtained from a series of pressure leaching trials showed that, by carrying out this reaction at above ambient oxygen partial pressures and at elevated temperatures, the corrosion rate can be significantly increased above that achieved in the conventional aeration process.