Journal of Electroanalytical Chemistry, Vol.397, No.1-2, 177-184, 1995
Electrodeposition of Zinc Plus Cobalt Alloys - Inhibitory Effect of Zinc with Convection and pH of Solution
The influence of pH and agitation on the electrodeposition of zinc + cobalt alloys from aqueous chloride solutions was studied on vitreous carbon electrodes paying special attention to the initial stages of the electrodeposition process. Several Zn(II)/Co(II) ratios in the solution were used, keeping the total concentration of metallic ions at 0.1 mol dm(-3) and chloride ion at 1 mol dm(-3). The presence of zinc in the bath always inhibited cobalt deposition, leading to anomalous co-deposition. For Zn(II)/Co(II) ratios lower than 1 and stationary conditions, inhibition disappeared after a certain time, leading to normal co-deposition. For a fixed Zn(II)/Co(II) ratio, the end of the inhibition was favoured when the pH of solution was increased. With rotating disk electrodes (RDE), co-deposition remained anomalous. Moreover, under conditions of normal deposition, the system could be returned to anomalous behaviour by convection using the RDE. Thus, the end of the anomalous codeposition was directly related to the depletion of Zn(II) in the environment of the electrode.