Effect of Mg~(2+) on the microstructure and corrosion resistance of the phosphate conversion coating on hot-dip galvanized sheet steel

摘要

The effect of Mg~(2+) in the phosphate solution on the microstructural evolution and corrosion resistance of the coating on hot-dip galvanized steel has been explored. Surface morphology observations reveal that increasing the solution Mg~(2+) concentration increases the population density and refines the grain size of the phosphate grains. In the presence of Mg~(2+), the phosphate coating is composed of mixed Zn phosphate hydrate and (Zn, Mg) phosphate hydrate. Furthermore, elevating Mg~(2+) in the solution reduces the porosity of the phosphate coating. As a result, the corrosion resistance of the phosphate coating is improved.