Effect of a small amount of Mo, W and Sn additives on the morphology and orientation of electrodeposited Zn

Zn electrodeposition was carried out on a steel sheet galvanostatically at 1500 A/m² in an agitated sulfate solution of pH 2 at 40°C to investigate the effect of a small amount of Mo, W and Sn additives on the morphology, crystal orientation and lightness of deposited Zn. No Mo and W codeposited with Zn, and hardly showed any effect on the morphology of deposited Zn. Mo and W increased the orientation of (0001) plane of Zn irrespective of not changing the overpotential for Zn deposition. Sn codeposited with Zn, and the platelet crystals of Zn was disappeared. Sn increased the crystal orientation of (0001) and (1013) plane of Zn due to a decrease in overpotential for Zn deposition. The lightness of deposited Zn depended on the crystal orientation and surface roughness of Zn. At coating weight of 20g/m², Sn, Mo and W enhanced the lightness of Zn due to an increase in orientation of (0001) and (101̄3) plane. However, with increased coating weight, since the surface roughness became large by addition of Mo, W and Sn, the enhancement of lightness by an increase in (0001) and (101̄3) plane was canceled.