EVALUATION OF SOME NEW ORGANIC ADDITIVES WITH ALTERNATIVE FUNCTION GROUPS IN CYANIDE-FREE ALKALINE ZINC ELECTROPLATING

Polymers (I and II) have been prepared based on imidazole and epichlorohydrine. These polymers were used as primary additives in non cyanide alkaline zinc electroplating processes at ambient temperature. At the same time new low molecular weight compounds were used as secondary additives to increase brightening such as pyridinium salts and aromatic aldehyde derivatives. Pyridinium salts were prepared based on pyridine and nicotinic acid while the aldehyde derivatives were based on vertraldhyde and benzaldehyde. The structure of the primary and secondary additives was designed to have different function groups to study the effect of their changing on plating quality such as hydroxyl, carboxylic and sulphonic groups. Concentrations of primary and secondary additives were changed as well as cell current and platting time in order to find the best combination to ensure full brightness. Moreover a try to combine 3 additives with these alternative function groups were performed for a better brightness and uniformity.