Influence of glycerol, mannitol and sorbitol on electrodeposition of nickel from a Watts bath and on the nickel film morphology

The electrodeposition of nickel on to platinum substrate in a Watts bath in the presence of glycerol, mannitol or sorbitol has been studied. The presence of polyalcohols in the electrolytic solution proved to be significant since deterioration of the bath contents during operation was not observed. The influence of the concentration of these compounds on the nickel deposition process and on the nickel film morphology was investigated by voltammetric and scanning electron microscopy (SEM) techniques, respectively. Voltammetric studies of these baths showed that additives influence the kinetics but not the thermodynamics of the deposition process. The current efficiencies of the plating baths containing polyalcohols were high (∼ 95%). Clear and bright electrodeposits were successfully obtained from these baths even in the region of high hydrogen evolution, suggesting that the additives prevent the deposits becoming darker. According to the SEM results, the presence of these additives in the nickel plating bath was beneficial, since nickel films without cracks were obtained. In particular, glycerol (at 0.39 M and at − 1.6 V) showed good leveling properties as it gave the smoothest film. EDS analysis leads to infer that carbon has not been probably incorporated in the nickel films.