Mg含量对真空蒸镀Zn-Mg镀层耐蚀性的影响

Effect of Mg Content on the Corrosion Resistance of Zn-Mg Alloy Coatings Deposited by Vacuum Palting

采用盐雾试验及电化学方法等对真空蒸镀Zn-Mg合金镀层的显微组织及耐蚀性进行了研究。结果表明,Mg的质量分数为4.5%时,Zn-Mg合金镀层具有较好的耐蚀性,此镀层经过720h盐雾试验后仍未出现红锈,耐蚀性至少是纯Zn镀层的9倍。XRD结果表明Zn-Mg合金镀层中存在能够提高耐蚀性的MgZn2相和Mg2Zn(11)相,其经过盐雾腐蚀后的腐蚀产物主要为氧化锌(ZnO)、碱式氯化锌[Zn5(OH)8Cl2·H2O]、碱式碳酸锌[Zn4CO3(OH)6·H2O]和Zn5(CO3)2(OH)6等。Zn5(OH)8Cl2·H2O致密且绝缘性好,能抑制阴极反应和疏松ZnO的形成,从而使得Zn-Mg合金镀层具有优异的耐蚀性。

Microstructure and corrosion resistance of vacuum-evaporated Zn-Mg alloy coating were studied by salt spray test and electrochemical methods.The results show that when the mass fraction of Mg was 4.5%,the Zn-Mg alloy coating had relatively good corrosion resistance.After 720h of salt spray test,no red rust appeared on the surface of the coating,and the corrosion resistance of the coating was at least 9 times that of the pure Zn coating.XRD analysis showed that MgZn2 phase and Mg2Zn11phase which could improve the corrosion resistance appeared in the coating.After salt spray corrosion,the corrosion products on the coating surface were mainly zinc oxide(ZnO),basic zinc chloride[Zn5(OH)8Cl2·H2O],basic zinc carbonate[Zn4CO3(OH)6·H2O]and Zn5(CO3)2(OH)6etc.Zn5(OH)8Cl2·H2O was dense and had good insulating properties,which could inhibit the cathodic reaction and the formation of loose ZnO,so that the Zn-Mg alloy coating had excellent corrosion resistance.