Corrosion resistance of Zn-Al-Mg alloy coatings with different thicknesses
[Introduction]Zn-Al-Mg alloy coating is a new type of coating with excellent corrosion resistance,which is related to its thickness.[Method]The corrosion resistance to neutral salt spray of the steels coated with 80,120,and 180 g/m2 of Zn-Al-Mg alloy (coded as ZM80,ZM120,and ZM180,respectively) was compared by glow discharge spectrometry (GDS),scanning electron microscopy (SEM),and electrochemical measurements.[Result]Red rust occurred on ZM80,ZM120,and ZM180 after neutral salt spray test for 504,840,and 1200 h,respectively. The corrosion of the Zn-Al-Mg alloy coated steel underwent four stages including protection of passivation film,barrier of zinc coating,galvanic protection of zinc coating,and corrosion of steel substrate. The protection of passivation film is closely related to its uniformity. The red rust areas of scratched ZM120 and ZM180 specimens were not significantly different from that of the unscratched ones at different stages of neutral salt spray test,which is mainly due to the fact that the compact corrosion products forming at the damaged position of Zn-Al-Mg alloy coating slow down the corrosion process.[Conclusion]Zn-Al-Mg alloy coatings with different thicknesses feature different anticorrosion property. It is better to determine the coating thickness according to the application scenarios.
zinc-aluminum-magnesium alloycoating thicknessred rustcorrosion productpassivation film
万方数据
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