镁合金高压阳极氧化工艺研究

Study of High-Voltage Anodizing Technology for Magnesium Alloy and Properties of the Anodized Film

为开发耐蚀性能优良的镁合金阳极氧化工艺，用正交试验对AZ91D镁合金高压阳极氧化成膜工艺进行了研究，并利用扫描电镜（SEM）、X射线衍射（XRD）、X射线光电子能谱（XPS）、全浸腐蚀试验和极化曲线等分别研究了镁合金阳极氧化膜层的表面形貌、相成分、元素成分、价态和膜层的耐蚀性等。获得了AZ91D镁合金高压阳极氧化的最佳成膜工艺参数为：10g／L KOH，5g／L NaF，5g／L Na2SiO3，0．5g／L Na2B4O7，100mL／L乙二醇，75mL／L丙三醇，50mL／L组分G；电流密度8．9mA／cm^2，氧化时间30min。在最佳工艺下所得阳极氧化膜层呈多孔结构，孔洞分布比较均匀，孔径尺寸约为1～2μm；氧化膜层主要由Al2SiO5、MgF2和MgAl2O4相组成；氧化膜层的耐蚀性明显优于传统含铬DOW17工艺所得氧化膜层的耐蚀性。

Orthogonal test was carried out to establish the optimal high-voltage anodizing technology for magnesium alloy, aiming at significantly increasing the corrosion resistance of the Mg alloy. The morphology, phase composition, valence of elements, and corrosion resistance of the anodic film were studied by means of scanning electron microscopy, X-ray diffraction, X-ray photoelectron spectroscopy, total immersion test, and polarization curve measurement. As the results, the optimized electrolyte was determined to be composed of 10 g/L KOH, 5 g/L NaF, 5 g/L Na_ 2SiO_ 3, 0.5 g/L Na_ 2B_ 4O_ 7, 100 mL/L glycol, 75 mL/L glycerine, 50 mL/L component G, while the optimal anodizing parameters were suggested as current density 8.9 A/cm 2 and anodizing duration 30 min. The anodizing film obtained at the optimal conditions had porous structure, and the pores uniformly distributed in the film had an averaged size about 1~2 μm. Moreover, the anodizing film was composed of Al_ 2SiO_ 5, MgF_ 2, and MgAl_ 2O_ 4, and showed much better corrosion resistance than the same anodizing film prepared using conventional Cr-containing DOW17 process.