The Pb oxide and Ru oxide films with various compositions were prepared by reactive sputtering using mixed gas of Ar and O2, and those anodic polarization properties were investigated in a 150 g L-1 H2SO4 solution at 303–333 K. When O2 amount of the Ar-O2 mixed gas was 25 vol.% or more, the product thin films were identified as mixed phase of α-PbO2 and β-PbO2 for the reactive sputtering of Pb target. On the other hand, the products were single phase of RuO2 for the reactive sputtering of Ru target at the same O2 amount of the mixed gas. The anode potential of the metallic Pb thin film was equal to that of the PbO2 thin film at the current density of 10 mA cm-2 or more. So, it can be judged that the surface of the Pb-based alloy anode was covered with the PbO2 at 60 mA cm-2, which is a typical current density during the operation of zinc electrowinning, and the oxygen evolution overpotential of the PbO2 determined the bath voltage of the electrowinning. Moreover, the anodic polarization measurement showed that the anode potential of the RuO2 at 60 mA cm-2 was about 560 mV lower than that of the PbO2. Therefore, the remarkable decrease of the anode potential for the Pb-based powder rolling anode, in which the RuO2 powders were dispersed in the Pb substrate, was probably due to an extremely low oxygen evolution overpotential of the RuO2 in itself.
