Influence of additives on the corrosion rate and oxygen overpotential of Pb–Co3O4, Pb–Ca–Sn and Pb–Sb anodes for copper electrowinning: Part II

The influence of two additives, BC-2 and TT, on the oxygen overpotential and corrosion rate of Pb–Co3O4, Pb–Ca–Sn and Pb–Sb anodes was investigated. At 25 °C, both additives depolarise oxygen evolution on the Pb–Co3O4 anode but not on Pb–Ca–Sn or Pb–Sb anodes. The additive TT results in the formation of a smaller amount of PbO2 on the anode compared with that formed in basic electrolyte (BE) or in the presence of BC-2. A slightly larger amount of PbO2 is formed on Pb–Ca–Sn or on Pb–Sb anode in the presence of BC-2 or TT. In the presence of BC-2 or TT, the amount of PbO2 formed on Pb–Co3O4 anode is approximately half that on Pb–Ca–Sn and Pb–Sb anodes. At 45 °C, the effect of TT on the Pb–Ca–Sn anode varies during prolonged polarisation. BC-2 depolarises oxygen evolution on Pb–Ca–Sn anodes and contributes to the formation of a larger amount of PbO2 on the anode, whereas for Pb–Co3O4, this reaction is polarised as compared to Pb–Ca–Sn. At 45 °C, as well at 25 °C, the amount of PbO2 formed on Pb–Co3O4 is approximately half that formed on the Pb–Ca–Sn anode. The corrosion rate of the Pb–Co3O4 anode is lower than the Pb–Ca–Sn anode under these conditions. Both additives modify the structure of the anodic layer on Pb–Co3O4, Pb–Ca–Sn or on Pb–Sb anode.