Corrosion and passivation behavior of noble metal coated anodes in copper electrowinning applications

The performance of platinum/iridium coated titanium anodes under electrolytic conditions typical of those encountered in copper electrowinning applications has been studied. The corrosion loss of coating totalled approximately 1.5 μg/A · h during normal operation with a preferential loss of platinum from the coating. Anode potentials were observed to increase with time and the onset of complete electrode degradation was accompanied by a large increase of anode potential together with a loss of coating by spalling. The mechanism of coating loss and anode degradation is discussed.