Kinetics of gold and a gold-10% silver alloy dissolution in aqueous cyanide in the presence of lead

The influence of lead additions on the anodic behaviour of gold and a gold-silver alloy in cyanide solution and on the cathodic reduction of oxygen on these metals was studied using potentiodynamic polarization measurements. It was found that lead additions increased the anodic activity of the gold, as well as that of the gold-silver alloy just positive of the open circuit potential, but only that of the gold-silver alloy at more positive potentials. However, lead additions also increased the rate of oxygen reduction on both metals, such that the dissolution rate, as predicted using the mixed potential theory, increased significantly with lead additions; this increase in rate was the result of the increase in the rate of the reduction of oxygen rather than the increase in the anodic activity of the alloys.