Influence of anodic pulses and periodic current reversion on electrodeposits

Abstract

This paper discusses how anodic pulses and periodic current reversion influence electrodeposition. Depending on the involved metal and electrolyte, very different effects can be observed and taken advantage of. The Wagner number, Wa, describing the current distribution is shown to be useful for predicting the throwing power at low frequencies of current reversion, even in complex electrochemical systems, but is less useful at higher frequencies. Passivation can occur due to oxide formation, super-saturation of metal salts or depletion of complexing agents at the electrode surface. Furthermore, dissolution and desorption processes in the anodic period can have strong influence on the succeeding cathodic electrocrystallisation affecting preferred crystal orientation, intrinsic stress and current efficiency. A literature survey is combined with experiments from silver plating from a cyanide bath.

Keywords:

• Pulse reverse
• Periodic current reversion
• Silver
• Throwing power
• Passivation
• Internal stress

Acknowledgements

The authors are grateful to the Swedish Knowledge Foundation (contact no. 20120184) and VINNOVA via M-ERA.NET Transnational Call 2012 for financial support. This paper is based on a presentation given at the Sixth European Pulse Plating Seminar, Baden, Austria, 7 March 2014.