Effect of Surface Textures of Steel Sheets on the Crystal Orientation of Electrodeposited Zinc

Prior to electrodeposition, steel sheets underwent polishing using emery paper, buff, and then electrolytic polishing. Zn deposition was performed galvanostatically at 1500 A/m2 in an agitated sulfate solution at 40°C to investigate the effect of the surface textures of steel sheets on the crystal orientation of Zn. The strain of the steel surface and the decrease in Fe grain size due to this strain were largest with emery paper polishing, then with buff polishing, then when unpolished, and were smallest after electrolytic polishing. The preferred orientation of the {0001} Zn basal plane of the hcp structure was largest with electrolytic polishing, and decreased in the following order: unpolished, buff polishing, and then with emery paper polishing. Thus, the preference of the {0001} orientation of Zn increased with decreasing the strain of steel sheets and increasing the grain size of Fe. With electrolytic polishing, the strain applied to the steel sheets was decreased, the grain size of Fe increased, and therefore the epitaxial growth of deposited Zn occurred easily. The initial Zn deposits appeared to grow epitaxially as indicated by the orientation relationship of {111}Fe//{0001}Zn because the preferred orientation of the steel substrate used in this study is {111} Fe. The preferred orientation of {0001} Zn seems to be more common under conditions where the epitaxial growth of deposited Zn is easy to occur.