Silver Electrodeposition from Cyanide Solutions: Effect of Lead Ions

Abstract

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 Δt. Shown is that on the freshly renewed electrode (Δt<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 Δt required to achieve the same effect. These regularities are attributed to catalytic influence of lead adatoms, whose surface concentration depends on c1 and Δt, as well as on the intensity of their incorporation in the silver deposit.