Effect of adding sorbitol to the electroplating solution on the process of depositing lead on copper and the morphology of the film produced

The electrodeposition of lead on to a copper substrate from a plumbite solution, 0.1 M Pb(NO3)2 + 0.2 M sorbitol + NaOH, was investigated over a range of concentrations of the hydroxide. Interactions between the copper electrode surface and the lead deposit were investigated by the voltammetric technique. From these experiments, it was concluded that underpotential deposition (upd) of lead does not occur on copper and that lead nucleation occurs as soon as deposition is operative from −0.78 V. Energy-dispersive X-ray spectroscopy (EDS) and scanning electron microscopy (SEM) of the lead films corroborates this result. Lead films obtained at −0.78 and −0.90 V were adherent and could be used as a support in battery plates, but this adhesion of lead to copper cannot be attributed to upd. SEM analysis showed that films produced at potentials down to −0.90 V were smooth and that this is the critical potential for a transition from dense to pyramidal or dendritic crystals patterns. The dendritic crystallites can be transformed into a high-purity lead powder.