Zn was electrodeposited galvanostatically on a steel sheet at 1 500 A/m2 in an agitated sulfate solution of pH 2 at 40°C to investigate the effects of small amounts of Mo, W, or Sn additives on the morphology, crystal orientation and lightness of the deposited Zn. Neither Mo nor W codeposited with Zn, and both showed hardly any effect on the morphology of the deposited Zn. Mo and W increased the orientation of the (0001) plane of Zn, but did not change the overpotential for Zn deposition. Sn codeposited with Zn and, as a result, platelet crystals of Zn did not form. Sn increased the crystal orientation of the (0001) and (101̄3) planes of Zn as a result of a decrease in the overpotential for Zn deposition. The lightness of the deposited Zn depended on its crystal orientation and surface roughness. At a coating mass of 20g/m2, Sn, Mo and W enhanced the lightness of Zn by increasing the orientation of its (0001) and (101̄3) planes. At higher coating masses, however, this enhancement in lightness disappeared as a result of the increase in surface roughness induced by the presence of the inorganic additives.
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