A new Zn-Ni-Cd plating process was developed which offers a unique way of controlling and optimizing the Ni and Cd contents in the final deposit. Zinc-nickel-cadmium alloy was deposited from a 0.5 M NiSO4 + 0.2 M ZnSO4 bath in the presence of 0.015 M CdSO4 and 1 g/L nonyl phenyl polyethylene oxide. Using this process a Zn-Ni-Cd ternary alloy, with a higher nickel content as compared to that obtained from conventional Zn-Ni baths, was synthesized. The Zn-Ni-Cd alloy coatings deposited from an electrolyte containing 0.015 M (0.3%) CdSO4 has a Zn to Ni ratio of 2.5:1. The increase in nickel content accounts for the observed decrease in the corrosion potential to a value lower than that of Cd but higher than the corrosion potential of iron. The coatings have superior corrosion resistance and barrier properties than the typical Zn-Ni and cadmium coatings. Polarization studies and electrochemical impedance spectroscopy analysis on Zn-Ni-Cd coatings show a barrier resistance that is ten times higher than that of a conventional Zn-Ni coating.
Journal of the Electrochemical Society, 2000, pages 1781-1786.
© The Electrochemical Society, Inc. 2000. All rights reserved. Except as provided under U.S. copyright law, this work may not be reproduced, resold, distributed, or modified without the express permission of The Electrochemical Society (ECS). The archival version of this work was published in the Journal of the Electrochemical Society.
Publisher's link: http://dx.doi.org/10.1149/1.1393434