铝阳极氧化膜的硫酸钇脉冲封闭

Anodic Aluminum Films Sealed by Sulfate Yttrium With Pulse Current

研究了硫酸钇脉冲封闭对工业纯铝阳极氧化膜受热开裂行为及电化学行为的影响。利用扫描电子显微镜(SEM)观察了沸水封闭和钇盐脉冲封闭后阳极氧化膜的表面和截面形貌。利用电化学交流阻抗谱(EIS)和极化曲线研究了两种封闭方法的电化学腐蚀行为。结果表明,通过硫酸钇脉冲封闭,可以将钇元素引入到氧化膜中。与沸水封闭氧化膜加热后表面出现了宽度达1μm的粗大的裂纹相比,硫酸钇封闭的氧化膜表层更加致密,其多孔层孔壁的加粗、孔隙减小,氧化膜显微硬度明显提高,使得氧化膜在加热后仅出现一些细小的微裂纹。从交流阻抗结果可以看出,硫酸钇封闭氧化膜的Rp值是沸水封闭氧化膜的1.43倍,极化曲线结果表明,经过钇盐封闭后,氧化膜的自腐蚀电位比沸水封闭的试样正移约280mV,自腐蚀电流密度降低为沸水封闭试样的0.41。钇盐封闭的氧化膜在NaCl溶液中的耐蚀性能也有显著提高。

A sulfate yttrium sealing method with pulse current was applied on anodic film of aluminum alloy and the cracking, and electrochemical performance of the anodic film was studied. The surface and section micrographs of oxide film were captured with a scan electron microscope （SEM）. Electrochemical impedance spectroscopy （EIS） and polarization curve measurements were used to study the electrochemical corrosion behavior of the sealed oxide film. The results revealed that yttrium was introduced into the anodic film by the method. In contrast to the film sealed in boiling water, the anodic film sealed in yttrium sulfate solution is more compact with thicker pore walls and smaller pores on the surface, and the microhardness of the film is increased, leading to few tiny cracks on the surface, while there are wide cracks which reach 1 um approximately on the surface of film sealed in boiling water. Electrochemical impedance spectroscopy （EIS） showed Rp of film sealed in yttrium sulfate is 1.43 times of that of film sealed in boiling water. Polarization curves showed the corrosion potential of film sealed in yttrium salts is 280 mV, more than the one in boiling water, and corrosion current density of film sealed in yttrium salts is 0.41 times of that in boiling water. The film in NaCl solution also shows better resistance to cracking under heating condition.