AZ91D镁合金表面无铬化学转化膜的研究

Corrosion Resistance of Chemical Conversion Coating Layer with Chrome Free on AZ91D Magnesium Alloy

在AZ91D镁合金表面利用无铬的KMnO4-Mn(H2PO4)2-pH值调整剂转化液进行化学转化,分析了转化膜的形成机理。经XRD分析结果显示,转化膜为非晶态结构,SEM观察发现,转化膜表面均匀,存在有利于增强涂装层附着力的网状裂纹。转化膜经EDS和XPS分析表明,主要元素为Mg、Al、Mn、O,由MgO、Mg(OH)2、MgAl2O4、Al2O3、Al(OH)3、MnO2组成。转化后的AZ91D镁合金在3.5%的NaCl溶液中全浸试验结果表明,其腐蚀速率低于其他化学转化膜。

Chemical conversion coating with chrome free was prepared on surface of AZ91D magnesium alloy in phophate-permaganate-pH value additive solution. Forming mechanism of the conversion coating was observed by XRD (X-ray diffraction) and SEM (scanning electron microscope). The results shows that the chemical conversion coating exhibits amorphous structure with uniformly distributed composition in the surface, and the reticular crackle which is helpful for improving adhesive ability of coating can be observed. EDS and XPS analysis shows that the chemical conversion coating is composed of MgO, Mg(OH)2, MgAl2O4, Al2O3, Al(OH)3 and MnO2 phase. The corrosion resistance of the chemical conversion coating with chrome free is obviously superior to that of the others in 3.5%NaCl solution.