Pulsed Potential Dissolution Reduces Anode Residue Formation during Nickel Electroplating

Abstract

The electrodissolution of nickel pellets with different controlled electrical variables was investigated in an effort to mitigate anodic residue in Watts bath based electroplating cells. During galvanostatic dissolution the anode potential was seen to oscillate between passive and transpassive (pitting) potentials. In-situ microscopy and ex-situ characterization has shown that lacy-pit formation and large, partially perforated, pit covers formed during galvanostatic potential decay and contributed significantly to anode residue. Constant potential measurements at high potentials reduced the anode residue but require large power consumption. Current transients during potentiostatic pulses were analyzed and the critical time where pit propagation changed from superficial to quasi-hemispherical was determined. An alternative method of anode dissolution was devised using potential pulses and duty cycles that allowed average current densities comparable to industrial plating conditions to be achieved. By restricting the time spent at large positive potentials to 50 ms, anode residue was reduced more than six-fold in comparison to an equivalent galvanostatic dissolution run at a comparable current density.