A kinetic model for the anodic dissolution of zinc in alkaline electrolyte with sodium metasilicate additions

The anodic dissolution of zinc electrodes in potassium hydroxide solutions containing sodium metasilicate has been investigated experimentally and theoretically in this study. On the basis of the experimental results, a kinetic model based on a competitive chemisorption approach has been developed and tested. The steady-state dissolution of zinc electrodes in the above-mentioned system has been measured using rotating disc electrode techniques. Good agreement is obtained between the model and the experimental results. The activation energy for the system is close to that for a kinetically controlled mode. This suggests that a surface reaction is rate limiting during the electro-dissolution process. It has been shown that the increase in the Tafel slope for the above-mentioned system in the active dissolution region is due to the adsorption of silicate on the electrode surface. A modified Langmuir model has been found to work reasonably well for the system studied. A change in the reaction order with respect to hydroxide ion has been found experimentally and predicted by the model also. Copyright (C) 1996 Elsevier Science Ltd