Mg对Galvalume镀层微观结构、耐蚀性和成形性的影响

利用扫描电镜、X射线衍射仪、电化学测试和杯突试验研究了Mg(质量分数15%)对Galvalume(Zn-55Al-16Si)镀层微观结构、耐蚀性和成形性的影响.扫描电镜和X射线衍射仪检测结果显示，添加Mg后在Zn-55Al-16Si-15Mg镀层的枝晶间区出现了MgZn2相；腐蚀产物的微观形貌显示Mg能减少镀层腐蚀产物中的裂纹，并提高其致密性.电化学检测结果显示，Zn-55Al-16Si-15Mg镀层的腐蚀速度仅为Galvalume的341%，因此Mg能显著地提高Galvalume镀层的耐蚀性；MgZn2作为强化相，强化了镀层的枝晶间区，减少了成形杯弯曲外表面的微裂纹，显著地提高了Galvalume镀层的成形性.

Effects of Mg on the Microstructure, Corrosion Resistance and Formability of Galvalume Coatings

By means of scanning electronic microscopy (SEM)， X ray diffraction (XRD)， electrochemical test and cupping test， the effects of Mg (15 wt.%) on the microstructure， corrosion resistance and formability of Galvalume(Zn 55Al 16Si) coating were studied. The SEM and XRD results revealed that MgZn2 phases appeared in the zinc rich interdendritic area of Zn 55Al 16Si 15Mg coating. The morphology of the corrosion product showed that magnesium eliminated the cracks in the corrosion product of Galvalume coating and enhanced the compactness of the corrosion product. The results of the electrochemical test showed that the corrosion rate of Zn 55Al 16Si 15Mg coating was 341% of that of Galvalume coating， which means that the addition of magnesium markedly improved the corrosion resistance of the Galvalume coating. As a strengthening phase， MgZn2 strengthened the zinc rich interdendritic area of the coating and decreased the cracks in the outer bending surface of the formed cup. As a result， the formability of Galvalume coatings was improved significantly.