Composition and morphology of Zn-Co alloy coatings deposited by means of pulse plating containing reverse current

The influence of bath constituents and pulse parameters on cobalt content, surface morphologies and grain size of Zn-Co alloy deposits was studied using a pulse plating technique with a square-wave current containing reverse pulse. It is found that Zn-Co alloy coatings obtained from the bath with the cobalt ion concentration over 60 wt% have a higher cobalt content in deposits. The results of pulse plating show that the average current density and reverse anodic current density amongst the variables investigated have very strong effects on the cobalt content in the Zn-Co alloy deposits. It is possible to clectrodeposit Zn-Co alloy coatings with 10-90 wt% cobalt by modulating pulse parameters. The grain size, surface appearance and internal stress in the deposit were improved significantly by introducing the reverse current.