The effects of sodium metasilicate on the electrodissolution of zinc in alkaline solutions

The electrochemical characteristics of zinc electrodes in potassium hydroxide solutions containing sodium metasilicate in the prepassive region were studied using the rotating ring-disk technique. Slow linear potential sweeps, impedance spectra, Gorbachev's temperature-kinetic method, and collection efficiency measurements were employed to examine the processes involved in the electrode reactions. It was found that the dissolution reaction was inhibited by the addition of silicate. The presence of silicate introduced additional irreversibility into the electrode processes and the controlling mechanism gradually shifted toward a more diffusion-controlled mode as the silicate concentration increased. Experimental data revealed that the electrode processes at the first and the second peaks are mixed control kinetics and that sodium metasilicate may interfere with the electrode kinetics.