Corrosion behaviour and catalytic effectiveness of Pb–Ca–Sn,RuO 2 –IrO 2 /Ti and IrO 2 –Ta 2 O 5 /Ti anodes for copper electrowinning

Abstract

The dependence of the corrosion rate on cell current density (CD) for three anode materials (Pb–Ca–Sn, RuO₂–IrO₂/Ti and IrO₂–Ta₂O_5/Ti) in a laboratory scale copper electrowinning cell has been studied by means of short term weight loss tests, scanning electron microscopy observations and energy dispersive spectroscopy analysis. The lead anodes (Pb–Ca–Sn) corroded at all the studied cell CDs, and their corrosion rate increased with increasing cell CD. The precious metal oxide anodes (RuO₂–IrO₂ and IrO₂–Ta₂O₅) only exhibited corrosion at the highest tested cell CD (1000 A m⁻²), and their corrosion rates were about a quarter of the lead corrosion rate at the same cell CD. The electrocatalytic properties of the three anode materials were characterised by means of potentiodynamic experiments. The overall results pointed to IrO₂–Ta₂O₅/Ti as the best anode material of choice, although plant tests would be required before deciding on any specific commercial use.