SiCp/2024 Al复合材料阳极氧化膜的结构和耐蚀性

用动电位阳极极化和点滴法评估了17％SiCp／2024Al复合材料(MMC)硫酸阳极氧化膜的耐蚀性，用光学显徽镜、SEM和TEM对氧化膜的形貌和结构进行了观察，用EDXS分析了膜的组成，极化实验结果表明，复合材料的阳极氯化膜具有良好的耐NaCl溶液腐蚀的能力，其腐蚀速度较未处理的基体降低了2个数量级以上。SEM形貌表明，SiC颗粒对膜的生长有阻碍作用，低电流密度下形成的阳极氧化膜膜层较薄，结构致密，孔隙细小，腐蚀实验结果表明该膜层具有更高的耐蚀性，TEM显示，MMC阳极氧化膜的孔隙分布严重不均，在SiC颗粒周围的基体中，孔隙密度较大，孔隙间距较小，孔径也较大，最大可达50nm，这表明阳极氧化膜具有低抗蚀性的结构特征，EDXS分析表明SiC颗粒在阳极氧化过程中会被氧化。

MICROSTRUCTURE AND CORROSION RESISTANCE OF ANODIZED FILM ON A SiCp/2024 Al METAL MATRIX COMPOSITE

The corrosion resistance of anodized 17% SiCp/2024 Al metal matrix composite (MMC) was evaluated using potentiodynamic polarization and the drop test. The morphologies and microstructures of the anodized film were observed with optical microscope, SEM and TEM. The film composition was analyzed by EDXS. The polarization results show that the anodized film provides satisfactory corrosion protection in 3.5% NaCl aqueous solution, and its corrosion rate is more than 2 orders of magnitude lower than that of the untreated sample. SEM morphologies show that SiC particles can hinder the growth of the film. The thickness of the film formed at low current density of 5 mA/cm2 is thinnest, its structure is compact, pores are small in size, and the film exhibits much better corrosion resistance. TEM observation indicates that the pores near SiC particles are more in quantity and bigger in average size than that away from SiC, the biggest size of pore is about 50 nm. This shows that the film on anodized MMC possesses the microstructural features of lower corrosion resistance. EDXS shows that part of the SiC particle could be oxidized when the MMC was anodized in H2SO4 solution.