THE EFFECTS OF SUBSTRATE MATERIAL ON THE MICROSTRUCTURE OF PULSE-PLATED ZN-NI ALLOYS

The effect of substrate material on the microstructure (surface morpho logy, phases present and preferred :orientation) and chemical composit ion of Zn-Ni alloy electrodeposits, produced from a chloride-based ele ctrolyte using the square-wave pulse-plating technique, has been inves tigated. Steel and commercial-purity, cold-rolled copper substrates we re considered. The results indicated that changing from a steel to cop per substrate does not have a significant influence on the deposit cha racteristics, except for the variations in the chemical composition. T hese variations were attributed to a number of factors including; (1) the different initial electrode potential (open circuit potential); (2 ) differences in cell voltages due to different electrical resistivity of the two metals; and (3) possibly to surface energy considerations. Because of the similar microstructure obtained, these coatings should have similar properties. (C) 1997 Elsevier Science S.A.