Passivation of Zinc Anodes in Alkaline Electrolyte: Part II. Influence of Operation Parameters

On the basis of a previously developed measurement method [M. Bockelmann, M. Becker, L. Reining, U. Kunz, and T. Turek, J. Electrochem. Soc., 165 (13), A3048 (2018)] the influence of current load interruptions, KOH electrolyte composition, temperature, and forced electrolyte convection on the anodic passivation of zinc was investigated in this study. Our aim was to find appropriate experimental conditions which could allow a long-term usability of the zinc anode without formation of passive films. We found out that interruptions lasting several minutes during galvanostatic dissolution of zinc, as well as increasing temperature and raising concentration of OH- ions in the electrolyte, effectively prolonged the service life of the electrode, but could not fully prevent it from passivation. On the contrary, increasing concentration of zinc oxide in the electrolyte enhanced the direct oxidation of zinc. However, application of sufficiently strong electrolyte convection and electrode overpotentials below a limiting value of about 0.1 V, allowed for electrode dissolution times of more than 1000 minutes without any indication of passive film formation. Therefore, the passivation of zinc anodes can be effectively avoided in cells with forced electrolyte convection and limited current densities. (C) 2019 The Electrochemical Society.