抄録
Zn-Cr electrodeposition behavior was studied in the sulfate solutions containing acyclic polymer additives such as gelatin and polyethylene glycol (PEG) at 2kA/m2. The electroreduction of Cr ions into metal was promoted by the addition of gelatin as well as PEG to the solution, and the deposits contained Cr in both trivalent and metallic states. The ratio of metallic Cr to total Cr changed depending on the molecular weight and the concentration of gelatin and PEG added to the electrolytic solution. Further, the cathode potential shifted to the less noble direction with increasing molecular weight or concentration of these additives. The ratio of metallic Cr in deposits showed a close relation with the cathode potential, and reached a maximum value at approximately −1.2V (vs. NHE). At potentials less noble than −1.2V, the deposits contained a considerable amount of trivalent Cr, which was the product of hydrolysis resulting from the accelerated hydrogen evolution by both the decomposition of water and the decrease in overpotential for hydrogen due to increase in Cr content in deposits.
