Mg对Zn-6Al镀层凝固组织的影响及耐腐蚀性的研究
The Effect of Mg Addition on the Solidification Structure and the Corrosion Resistance Property of the Zn-6%Al Alloy Coating
童晨1，苏旭平2，王建华2，吴长军2
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作者单位：1.) 湘潭大学 材料设计及制备技术湖南省重点实验室
2.) 常州大学 先进金属材料常州市重点实验室
中文关键字：热浸镀锌；锌铝镁；凝固组织；耐蚀性；腐蚀产物
英文关键字：hot-dip galvanizing; Zn-Al-Mg; Solidification structure; corrosion resistance; corrosion products
中文摘要：本文通过实验研究了不同含量Mg对Zn-6%Al合金镀层凝固组织及其耐腐蚀性能的影响。实验结果表明，Mg对合金镀层凝固组织和耐腐蚀性影响明显，当Mg含量在3%以内时，随着Mg含量的增加，镀层凝固组织中出现了耐腐蚀相MgZn2，晶粒不断细化，形成了Zn/Al/MgZn2三元共晶，并且随着Mg含量升高更加均匀致密，镀层的耐腐蚀性不断增强；当Mg含量达到3%时，镀层的耐腐蚀性能最好；Mg添加量超过4%后，镀层耐蚀性有所下降，镀层会出现漏镀等质量缺陷。XRD分析表明，含Mg镀层表面经过盐雾腐蚀后主要形成具有优良耐腐蚀性能的腐蚀产物Zn5(OH)8Cl2•H2O，Mg促进了腐蚀产物Zn(OH)2向Zn5(OH)8Cl2•H2O的转变，有利于镀层耐腐蚀性能的提高。
英文摘要：The present work investigated the effect of Mg addition on the solidification structure and the corrosion resistance property of the hot-dip Zn-6%Al alloy coating. The experiment revealed that the addition of Mg evidently effected the structure and morphology of the coating, with the additive quantities of Mg in the alloy coating from 0.1wt% to 3%, hard and brittle MgZn2 phase and the Zn/Al/MgZn2 ternary eutectic presented in the coating. As the addition of Mg refine the grains and make the eutectic more regular and denser, the corrosion resistance of the alloy coating enhance with the increasing of the Mg in coating. The Zn-6%Al-3%Mg has excellent corrosion resistance in all samples. As the content of the Mg is more than 4% in the alloy, the corrosion resistance and the surface quality decreases. The results of the XRD show that corrosion product of Zn-6%Al-3%Mg alloy coating is mainly Zn5(OH)8Cl2•H2O. The characteristic of Zn5(OH)8Cl2•H2O is dense, insoluble and short of electric conductivity. Since the addition of Mg promotes formation of Zn5(OH)8Cl2•H2O, Mg in the coating will improve the corrosion resistance of Zn-Al alloy coating.