Effects of number of substituents and molecular weight of polyamines on the non-cyanide alkaline zinc plating process

Abstract

The effects of the number of substituents and molecular weight of polyamines in the non-cyanide alkaline plating bath on cathodic polarization, cyclic voltammogram, morphology, brightness and bright ranges of zinc electrodeposited coating were investigated. Cathode polarization measurements showed that the polyamines all increased cathode polarization of the plating process. In addition, cyclic polarization curves of the 5 cycles also showed that adsorption and desorption of these polyamines were stable in the plating process. The Hull method pointed out that these polyamines created semi-bright ranges in the low current density. Morcover, the polyamine Bt-700 had the strongest effects on the brightness of the deposits at almost whole range of current density if its concentrations was sufficient. Surface morphology also showed that adding these polyamines made the crystals of deposits fine, smooth and uniform which agreed with increasing cathodic polarization.