镁合金AZ91D在氯化钠溶液中的腐蚀行为

Corrosion Behavior of Magnesium Alloys AZ91D in NaCl Solution

通过容量法、失重法和电化学阻抗谱(EIS)方法研究了镁合金AZ91D铸件及压铸件在5%氯化钠溶液中的腐蚀及电化学腐蚀行为。利用扫描电子显微镜(SEM)、能量色散谱(EDS)和X-射线衍射(XRD)方法研究了腐蚀产物表面形貌及其组成。结果表明:两种合金的腐蚀产物相同,由块状的化合物氢氧化镁[Mg(OH)2]和松枝状的水合氢氧化镁氯化物[Mg2Cl(OH)3.4H2O]组成;镁合金AZ91D压铸件的耐腐蚀性能比镁合金AZ91D铸件好;并通过浸泡过程中电荷转移电阻(Rt)和双电层电容(Y)的变化解释了两种合金的耐腐蚀性能差异。

Magnesium alloys have been used wide applications for their excellent properties, the corrosion and electrochemical behaviors of casting and die-casting Mg alloys AZ91D in 5% NaCl solution were investigated. The quantity of H2 gas evolution and mass loss were measured and both showed that the corrosion resistance of die-casting AZ91D was higher than that of casting AZ91D. This result was further proved by EIS and the difference of corrosion resistance between these two materials was also explained by monitoring R, and Y during immersion time. Whatever Mg alloys, major corrosion products were composed of ＇ nubbly＇ compound [ Mg （ OH）2 ] and ＇ pine needle＇ compound [ Mg2Cl（OH）3 · 4H2O].