氨基乙酸对镁-锂合金阳极氧化膜的影响

Effects of Aminoacetic Acid on Mg-Li Alloy Anodic Film

在镁-锂合金阳极氧化中以氨基乙酸为添加剂制取氧化膜,并讨论氨基乙酸对氧化膜结构、形貌及性能的影响。利用X射线衍射仪(XRD)、扫描电子显微镜(SEM)、无损涡流测厚仪、极化曲线(Tafel)和电化学交流阻抗谱(EIS)等分析了镁-锂合金基体和氧化膜的组成、表面形貌、厚度以及耐蚀性,并讨论其耐蚀机理。结果表明:阳极氧化膜主要由氧化镁、氢氧化镁和氢氧化锂构成;随着氨基乙酸的质量浓度的增加,阳极氧化膜趋于平整、致密,孔洞均匀;添加氨基乙酸形成的阳极氧化膜的自腐蚀电位正移,自腐蚀电流密度变小,当其质量浓度为6 g/L时,氧化膜耐蚀性最优,自腐蚀电流密度为1.12×10-7A/cm2;但当氨基乙酸的质量浓度过高时,氧化膜耐蚀性反而下降。电化学阻抗谱对氧化膜耐蚀性变化规律的分析与极化曲线结果相一致。

It is prepared magnesium-lithium alloy anodic films with aminoacetic acid as additive.The effects of aminoacetic acid on the microstructure,morphology and performance of the anodic film are discussed.The composition,surface morphology,thickness and corrosion resistance of the Mg-Li matrix and anodic film were analyzed with XRD,SEM,non-destructive eddy thickness meter etc.,and the corrosion resistance mechanism is also discussed.The results show that the anodic film is mainly composed of magnesia,magnesium hydrate and lithium hydrate;along with the increasing of the mass concentration of aminoacetic acid,the anodic film tends to be smooth and compact,with uniform pores;the self-corrosion potential of the anodic film formed by adding aminoacetic acid moves positively,as a result the self-corrosion current becomes smaller,when the mass concentration of the acid is 6 g/L,the corrosion resistance of the film is optimal,with a self-corrosion current density at 1.12×10^-7 A/cm^2.However,when the mass concentration of the acid is too high,the corrosion resistance of the film would contrary become worse.The analysis on the change law of the corrosion resistance of the film by electrochemical impedance spectroscopy is identical with the results gained from the polarization curves.