Influence of anodic pulses and periodic current reversion on electrodeposits

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.