Some Aspects of the Growth of Bronze Electrodeposits on Single Crystal Substrates

Summary

The growth of electrodeposited Cu-Sn bronzes on copper single crystals from a sodium-based cyanide-stannate electrolyte has been studied at constant potential at 65°C in a nitrogen-stirred cell. At 300 mV substrate continuation persisted to a greater thickness on copper surfaces with a [111] orientation than on those with either [110] or [100] orientations and random polycrystalline growth commenced earliest on the (110) face. The greatest extent of continuation of the substrate at higher overpotentials (450 and 600 mV) however, was observed on the (100) face. Again the least tendency for continuation of the substrate orientation was on the (110) face. This is in direct contrast to copper deposition from purified acid electrolytes where substrate continuation is most favoured by a [110] orientation and it is concluded that cyanides or other complexants present in the electrolyte alter crystal growth mechanisms due to adsorption. Twinning was found to be more prevalent in deposits formed at low overpotentials and this again may be due to adsorption. Observations concerning continuation of deposit growth on the (100) face of copper single crystals at 450 and 600 mV are in agreement with previous observations² concerning the growth and texture of bronze deposits on cube-textured copper cathodes.