Effect of Sr Element Content on the Microstructure and Corrosion Resistance of Zn-2%Al-1.2%Mg Coating

In order to further investigate the regulation of trace alloying elements on the microstructure of coatings and the mechanism of their influence on corrosion resistance， a dual plating method was used to prepare Zn-2.0%Al-1.2%Mg-x%Sr (x ＝0， 0.03%， 0.06%， 0.09%，0.12%， mass fraction) coatings on Q235 steel plates.The effects of Sr element content on the microstructure and corrosion resistance of Zn-2.0%Al-1.2%Mg coatings were examined through scanning electron microscopy (SEM)， X - ray diffraction (XRD) and 5%NaCl immersion test.Results showed that adding an appropriate amount of Sr element could effectively refine the primary η-Zn phase in the solidification microstructure of the surface of Zn-2.0%Al-1.2%Mg coating， promoted the formation of a Zn/Al/MgZn2 ternary eutectic structure， and made the FeAl3-Znx columnar crystals in the intermediate alloy layer denser.Notably， when the addition amount of Sr was 0.09%， the refinement effect of solidification structure on the surface of the coating was most obvious， an