Structure and Morphology of Zinc Rust Particles Prepared by Repeating Wet-Dry Cycles of Aqueous ZnCl₂ Solutions

Abstract

To simulate the atmospheric corrosion of galvanized steels in salinity environment, artificial zinc rust particles were prepared by repeating wet-dry cycle of aqueous ZnCl₂ solutions in the presence of zinc rusts such as ZnO and Hydrozincite （Zn₅（OH）₆（CO₃）₂: HZ）, and the transformation behavior of added ZnO and HZ into zinc hydroxychloride （Zn₅（OH）₈Cl₂･H₂O: ZHC） was examined. The procedure constitutes one cycle of wetting（20℃ and 4 h） and drying （85℃ and 20 h）. After 1 cycle, almost all the added ZnO and HZ were transformed into ZHC and its transformation rate was in the order of ZnO＞HZ. Increasing the wet-dry cycles enhanced the crystallization and particle growth of ZHC and turned the irregular-shaped ZHC particles into plate-like ZHC ones. These results allow us to infer that initial zinc rusts such as ZnO and HZ generated on the galvanized steels by atmospheric corrosion in salinity environment at initial corrosion stage are immediately transformed into plate-like ZHC rust particles, which form a dense protective rust layer on the steels to enhance the corrosion resistance.