Effect of Corrosion on the Composition of Pulse‐Plated Cu‐Ni Alloys

Abstract

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.Due to the importance of pulsed currents in alloy electrodeposition, 1-4 a variety of investigations have focused on determining the fundamental relationships between applied pulse-parameters, governing physical phenomena (such as reaction kinetics and hydrodynamics), and the composition of the deposit. Verbrugge and Tobias~'6 proposed a theoretical model which could be used to calculate current-voltage relationships, metal ion concentration at the cathode, and deposit composition during the electroplating of a multicomponent alloy using periodic currents. Their model included the equation of convective diffusion to describe liquid-phase mass transfer at a rotating disk, Butler-Volmer expressions to calculate the rate of chargetransfer reactions at the electrode surface, and activities of individual metals in the solid-state to compute the composition of the deposit. They investigated numerically the effect of hydrodynamics, reactant concentration, reversible potentials, and solid-state activity on the deposit composition of a Cd-Te alloy. Pesco and Cheh 7 used a treatment similar to that of Verbrugge and Tobias, except that solidstate activities were neglected. They computed the composition of Pb-Sn alloys plated at a rotating disk electrode under mixed mass-transfer and kinetic control. Ruffoni and Landolt ~ investigated experimentally the variation in the composition of Au-Cu-Cd alloys as a function of applied pulse parameters and hydrodynamics. The results were compared with the prediction of a mathematical model which took into account the kinetic behavior of the three alloy components and hydrogen. 9 More recently White and co-workers ~~ have presented a theoretical model which includes the effects of migration on ion transport and of addition agents on reaction kinetics of the depositing metals.During pulse-plating of binary a11oys, the applied current is cycled between a high and a low or zero value. At high current density, both alloying dements are reduced at the cathode, but at low current density or at the opencircuit potential the less noble metal can be selectively dissolved or displaced from the alloy by the more noble one. n46 The numerical analysis of Verbrugge and Tobias 5 has already indicated that the more noble component may contin...

In situ magnetization measurements of Cu/Co multilayers during the process of electrodeposition

“…This phenomenon has been shown to occur for Cu-Co and Cu-Ni layers pulse plated in galvanostatic conditions. 7,8 In our case we applied potential pulses, so the displacement is probably less important than in galvanostatic conditions. As shown in Fig.…”

Electrodeposition Science and Technology in the Last Quarter of the Twentieth Century

“…It has been found that displacement reactions during the off time can have an important effect on resulting alloy composition. 171 Theoretical models were proposed which take into account this effect and they were successfully tested with copper-nickel and copper-cobalt alloys. 172 Alloys for magnetic applications.-Electroplated alloys are widely used in magnetic read and write heads.…”

Nano-nickel–copper alloy deposit for improved corrosion resistance in marine environment

“…Ying et al (1988) developed a mathematical modelling for electrodeposition of nickel-copper alloy from citratebased solution; Podlaha et al (1994) also developed a mathematical modelling on influence of citrate complex in alloy deposition. Roy et al (1994), Bonou et al (1994) and Ghosh et al (1999) explained the corrosion resistance of the nickel-copper alloy deposited from both DC, pulse and reverse pulse techniques. Mohan and Rajasekaran (2011) studied the influence of electrolyte pH on the composition, corrosion resistance, and morphology of the nickel-copper alloy by brush plating.…”