烘烤对重铬酸盐封闭膜形貌和腐蚀行为的影响

铝合金阳极氧化后需进行封孔处理,烘烤极大的影响铝合金氧化膜的形貌和耐蚀性。本实验对2024铝合金阳极氧化经过重铬酸钾封孔处理后的膜进行烘烤研究。对烘烤过的试片与未烘烤的试片做电子显微镜表面形貌、激光共聚焦显微镜三维形貌及膜层的表面轮廓、膜的孔隙分布测试,且比较烘烤前后膜层的极化曲线。结果如下:铝合金阳极氧化重铬酸钾封闭后未烘烤膜的表面轮廓有很多非常深(深达18μm)、窄而细的孔,孔隙分布广而且密集;烘烤后封孔膜的孔隙深度降低,多孔层收缩变薄,孔隙分布稀疏。烘烤降低了重铬酸钾封闭膜的粗糙度且膜表面的凹坑有一定程度减少。从极化曲线看,烘烤后重铬酸钾封孔阳极钝化电流比未烘烤时低了几个数量级,说明烘烤提高了重铬酸钾封孔的铝合金的耐蚀能力。

Influence of Roasting on Morphology and Corrosion of Dichromate Sealed Films

After anodic oxidation of aluminum and aluminum alloy,the film should be sealed.The roasting process can extensively influence the structure and corrosion resistance properties of anodic oxidation film.The roasting effects on 2024 aluminum alloy anodic oxidation film sealed by K2Cr2O7 solution are researched.Influences of the roasting process on the film are drawn out through comparison of two-dimensional and three-dimensional morphologies,SEM morphologies,porosity,polarization curves of the roasted samples and unroasted ones.The conclusions are as follows: There are many deep(up to 18μm),small and narrow pores on the surface of the unroasted sample,they are dense and widely distributed.The depth of the pores on the film of the roasted sample reduced,and the porous layer contracted and became thinner,exiguous.The roughness and the concaves of the sealed film are reduced in some degree by the roasting process.It is seen from the polarization curves that the anodic passivation current of the roasted film is a several magnitudes lower than the unroasted one,so the corrosion resistance improved by roasting.