Cyanide-free silver electrodeposition with polyethyleneimine and 5,5-dimethylhydantoin as organic additives for an environmentally friendly formulation

The influence of polyethyleneimine (PEI) as additive for cyanide-free silver bath, in combination with 5,5-dimethylhydantoin (DMH) as complexing agent, is studied. Cyclic voltammetry (CV) measurements are used to characterize the electrochemical behaviour of the Ag/DMH complex. The Ag electrodeposition from the cyanide-free silver-plating bath is analysed by CVs and the process is optimized varying the PEI concentration. Chronoamperometry is then used to investigate the electrodeposition mechanism, which is found to be a three-dimensional diffusion-controlled nucleation and growth mechanism, according to the Scharifker-Mostany's model. Smoother, brighter and blue coloured silver deposits are obtained in the presence of PEI in a Hull's cell test, at low density current. Eventually, the influence of nitrate anion is also investigated. The presence of nitrate increases the range of current density allowing for an effective Ag deposition.