Electrochemical Properties and Microstructure of Al/Pb–Ag and Al/Pb–Ag–Co Anodes for Zinc Electrowinning

The Al/Pb–0.8%Ag and Al/Pb–0.75%Ag–0.03%Co (in mass fraction) anodes used in zinc electrowinning are prepared through the electrodeposition of lead methanesulfonate electrolyte onto an aluminum matrix. The results of anode polarization curves, Tafel curves, and EIS characterizations indicated that the Al/Pb–0.75%Ag–0.03%Co anode has higher electrocatalytic activity and corrosion resistance than the Al/Pb–0.8%Ag anode. SEM observations on the fruit surfaces demonstrated the crystals on the Al/Pb–0.8%Ag anode are larger than on the Al/Pb–0.75%Ag–0.03%Co anode. After 24 h of anodic polarization, SEM observations and XRD analysis showed that the MnO2–PbO2 layer on the Al/Pb–0.75%Ag–0.03%Co anode surface is characterized by dendritic crystals, and the PbSO4–PbO2 layer under the MnO2–PbO2 layer is characterized by uniform and chaotic orientation tetragonal symmetry crystallites of PbSO4. However, the MnO2–PbO2 layer on the Al/Pb–0.8%Ag anode surface is characterized by granular crystals, and the PbSO4–PbO2 layer under the MnO2–PbO2 layer is characterized by well-organized orientation crystallites of PbSO4, which are concentrated in certain zones.