A Study of the Electrodeposition of Bronze from a: Cyanide-Stannate Bath

Summary

A study of the electrodeposition of copper-tin bronzes has been made using a combination of polarization measurements, metallography, electron microscopy and electron probe microanalysis techniques. Total polarization curves have been measured at 40°-70°C and partial polarization curves calculated. At low cathode potentials only copper ion reduction takes place at all temperatures and at 40°-50°C reduction of stannate and hydrogen ions occurs almost simultaneously and a limiting current density for tin deposition is soon attained. Reduction of stannate ion commences at lower cathode potentials at higher temperatures and the limiting current density for tin deposition also increases with increasing temperature. The composition and microhardness of deposits have been determined as a function of current density and temperature, as have the cathodic efficiencies for copper and tin deposition. Deposits obtained at 5–15 mA/cm² have fine grained structures whereas those obtained at >15-20 mA/cm² have fine laminated structures. Electron probe microanalysis of layered deposits did not indicate compositional variations and preliminary studies using electron microscopy suggest that layer growth may be a structural rather than a compositional phenomenon.