Natural additive agents in the electrodeposition process have long been used to improve deposition flatness and help prevent impurities from precipitating during deposition. The effective molecular weight and elements of these natural additives during deposition, however, have not been clarified sufficiently to understand the mechanism behind their effectiveness.
In this research, we used gelatin having an average molecular weight of 18000, determined by HPLC, as a natural additive. We also used polyethylene glycol (PEG) having average molecular weights of 20000, 6000, and 2000 as a synthetic additive. Mass deposit changes were monitored by QCM.
We obtained the following results:
1) Mass change during deposition depended on the molecular weight of the additive.
2) The deposition rate in the presence of gelatin was lower than that in the presence of PEG.
3) Anomalous mass change was detected during deposition in the presence of gelatin and PEG additives. This corresponded to the change in the surface morphology of deposits.
