Influence of Mg on Corrosion Resistance of Hot-dip Zn-Al Alloy Coating

Zn-Al-Mg alloy coatings with different magnesium contents were prepared by hot dip method. Microstructures and compositions of the coatings were studied by SEM, EDS and XRD. NaCl solution immersion test, electrochemical thermal shock test were used to study the corrosion resistance of the coatings. The results show that the increasing of Mg contents can make the coating morphology more uniform and dense, improve the corrosion resistance in a certain range. Zn-Al-Mg alloy coatings with Zn-5% Mg-0.7%, showed the best corrosion resistance, the corrosion resistance became worse when the Mg content was beyond 0.7%.