Silver Electrodeposition from Cyanide Solutions: Effect of Lead Ions

Effect of lead hydroxy compounds on the process of electrodeposition of silver from cyanide electrolytes is studied on an electrode whose surface is renewed in solution by cutting off a thin layer of metal. This permitted to perform the study on both the freshly renewed electrode and at controlled values of the time of the electrode contact with solution t. Shown is that on the freshly renewed electrode (t<1 s) the presence in the solution of lead ions in concentrations c₁ on the order of 10^–5 M leads to the process depolarization only in the initial portion of a polarization curve. With c₁ increased to 10^–4 M the effect of depolarization extends on the entire polarization curve. Keeping the electrode in solution after the renewal of the metal surface magnifies depolarization, and the greater the concentration c₁, the shorter the time period t required to achieve the same effect. These regularities are attributed to catalytic influence of lead adatoms, whose surface concentration depends on c₁ and t, as well as on the intensity of their incorporation in the silver deposit.