Passivation of Zinc Anodes in  KOH  Electrolytes

Passivation times of horizontally upward‐facing and downward‐facing zinc microanodes in KOH electrolytes of five concentrations are reported. These measurements extend passivation data into a low current‐density region for evaluating conflicting interpretations of published work. To interpret our data, a new mechanism for anodic passivation is proposed. In high current‐density regions, passivation occurs when compact ZnO covers the electrode surface; in low current‐density regions, passivation occurs when the mass transfer of hydroxide ions across a porous ZnO layer is less than that required for anodization. This work also discusses passivation in porous zinc battery electrodes.