Review—Influence of Corrosion Reactions on the Pulse Electrodeposition of Metals and Alloys

Abstract

In the electrodeposition of metal and alloys by pulse plating, the importance of the pulse off-time is often neglected. Traditionally it is considered an electrochemically inactive period, allowing, for example, the relaxation of concentration gradients, desorption of additives, recrystallisation and discharge of the double layer capacitance. However, more recent studies have shown that it is possible to have corrosion processes occurring in the off-time which can significantly influence the deposit properties and current efficiency. This has been observed in both aqueous and non-aqueous systems, and appears a very general phenomenon. Typically, in these systems, corrosion is caused by dissolved oxygen or via comproportionation reactions. Similarly, during the pulse electrodeposition of binary and ternary alloys from aqueous and non-aqueous solutions, displacement (corrosion) reactions have been observed in the off-time that can alter the alloy composition and microstructure. The main aim of this paper is to review these various types of corrosion, establish the conditions under which they occur, and quantify their effects related to deposit characteristics, current efficiency and alloy composition.