研究出一种新的镁合金表面转化处理方法.其处理液由磷酸、硝酸盐、加速剂及成膜剂组成.原子力微镜（AFM）对这种转化膜的形貌观察表明，膜的表面光滑而有波浪起伏.用能谱仪（EDX）和X射线衍射谱（XRD）研究该膜结构和组成.EDX试验结果证明转化膜主要由Mg、 Al、Mn、P、Ca、O、K、Zn等元素组成.X射线衍射谱表明转化膜由非晶态物质与少量Ca0965Mg2Al6O27, Mn5.64P3,ZnAl2O4 和 (Mg0.66Al0.34)(Al0.83Mg0.17)2O4晶态化合物组成.运用电化学阻抗谱（EIS）和极化曲线试验研究了转化膜在NaCl溶液中的腐蚀过程,结果指出,转化膜表面Cl-吸附区的溶解快于非吸附区是转化膜产生点蚀的原因.
A chromium-free conversion coating treatment whose solution contains phosphate acid、 nitrate compound and accelerator was developed for magnesium alloy.The morphology of conversion was observed using AFM and SEM.The AFM results showed the surface of coating is smooth and slightly wavy.The structure and the composition were analyzed by using EDS and XRD.The EDX results indicated that the compositions of the coating were mainly compounds of Mg,Al,Mn，P，Ca and O.XRD result showed that coating layer contains amorphous materials and a small quantity of Ca0.965Mg2Al6O27,Mn5.64P3,ZnAl2O4 and (Mg0.66Al0.34)(Al0.83Mg0.17)2O4 crystalline compounds.Electrochemical impedance spectroscopy (EIS) and electrochemical polarisation was utilized to study the coating immersion in NaCl slution.The EIS and electrochemical polarisation results demonstrated that the reason for pitting corrosion of conversion coating is that dissolution at the chlorine anion absorbed area is higher than that of non-absorbed area.
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