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采用SEM、XRD、电化学方法和中性盐雾试验对热镀Zn-Al-Mg与GL镀层的组织和耐蚀性能进行了对比研究。结果表明,热镀Zn-Al-Mg镀层主要由纯Zn相、Zn-MgZn2二元共晶相和Zn-Al-MgZn2三元共晶相组成,镀层截面由枝晶状组织和合金层组成,枝晶状组织分布于镀层的整个截面上;电化学试验时镀层的电流密度较低,说明镀层中Al、Mg及MgZn2相的存在可以在镀层表面形成稳定的化合物,降低Zn的溶解速度,避免腐蚀的发生;共晶相可以使Mg元素在镀层中均匀分布,促使致密的碱式碳酸锌等腐蚀产物的生成,从而抑制阴极反应,增强热镀Zn-Al-Mg镀层的耐蚀性。
The microstructure and corrosion resistance of hot-dip Zn-Al-Mg and GL coatings were compared using SEM, XRD, electrochemical methods and neutral salt spray test. The results show that the hot-dip Zn-Al-Mg coating is mainly composed of pure Zn phase, Zn-MgZn2 binary eutectic phase and Zn-Al-MgZn2 ternary eutectic phase. The cross-section of coating is composed of dendritic structure and alloy layer. The crystalline structure distributes in the whole section of the coating. The electrochemical current density of the coating is low, indicating that the presence of Al, Mg and MgZn2 phases in the coating can form stable compounds on the surface of the coating, reducing the dissolution rate of Zn and avoiding corrosion The eutectic phase can make the Mg element distribute uniformly in the coating and promote the formation of corrosion products such as dense basic zinc carbonate, so as to suppress the cathode reaction and enhance the corrosion resistance of the Zn-Al-Mg coating.