Effect of Polyethylene Glycol on the Morphology of Zn Electrodeposited on Steel Sheet

Zn electrodeposition was carried out on a steel sheet galvanostatically at 1500 A/m2 in un-agitated sulfate solution of 40°C to investigate the effect of Polyethylene Glycol (PEG) addition on the morphology of Zn. In situ observation by atomic force microscopy showed that the growth of deposited Zn proceeded through the advance of macro-steps in platelet crystals to the [2130] direction. The addition of PEG to the solution brought about a decrease in size and macro-step height and an increase in inclination of platelet crystals of deposited Zn. In PEG-containing solution, the crystal orientation index of (0001)Zn decreased, while those of (1120), (1011), (1010)Zn correspondingly increased. This change in the crystal orientation generally corresponds to the macro morphology of deposited Zn. The surface roughness of initially deposited Zn was larger in PEG-containing solution than in PEG-free solution due to the decrease in orientation index of (0001)Zn. However, with increased coating weight, the roughness was smaller in PEG-containing solution due to the decrease in size of Zn platelet crystals.