EFFECT OF CORROSION ON THE COMPOSITION OF PULSE-PLATED CU-NI ALLOYS

Copper and nickel are codeposited by pulse and reverse-pulse plating on a rotating cylinder cathode from a citrate bath. Polarization data for copper and nickel as well as potential transients during pulse and reverse-pulse current experiments show that displacement reactions may occur during the pulse off time or pulse-reversal time. A mathematical model which includes this effect is developed to predict the composition of electrodeposited alloys. The model shows that copper deposits at the mass-transfer limiting current throughout the pulse-cycle while nickel is alternately deposited and dissolved during the pulse on-time and off-time (or reversal time). The alloy composition is governed by pulse parameters and the diffusion limiting current for copper deposition.