工作电压对微弧氧化6061铝合金耐腐蚀性能的影响

Effect of Working Voltage on Corrosion Resistance of Micro-Arc Oxidation of 6061 Al-Alloy

【目的】为提高铝合金的耐腐蚀性能,采用交流恒压微弧氧化方法在6061铝合金表面制备金属陶瓷涂层并研究了工作电压对涂层性能的影响。【方法】采用XRD分析、SEM微观组织形貌观察、交流阻抗(EIS)测试和涂层厚度分析等方法,测试工作电压对涂层生长、物相组成、耐腐蚀性能等的影响,分析其影响机理。【结果】6061铝合金微弧氧化涂层表面为疏松多孔的"火山口喷射"形貌,当工作电压小于450V时,涂层的厚度随着工作电压的增加而增大,火山口状放电孔数增加,涂层主要相为β?Al2O3和少量α?Al2O3;工作电压大于450V后,火山口状放电孔数减少而孔径增大,并且工作电压增大到500V时涂层开始出现微裂纹,耐腐蚀性先增强后减弱。【结论】工作电压为450V时制备的涂层,疏松层放电微孔电阻Rp和基体金属腐蚀反应的电荷转移电阻Rct分别为2.875×106Ω·cm2和7.575×106Ω·cm2,比制备的其他涂层具有更好的耐腐蚀性能。

【Objective】In order to enhance the corrosion resistance of Al-alloys,the ceramic coating on the surface of 6061 Al-alloy were prepared by micro-arc oxidation(MAO),in constant pressure AC mold.The effect of working voltage on the corrosion properties of MAO coatings was studied.【Methods】Scanning electron microscopy(SEM),X-ray diffraction(XRD),electrochemistry impedance spectroscopy(EIS)and coating thickness tests were used to the influence of working voltage on coating growth,phase composition and corrosion resistance,and the influence mechanism of working voltage was analyzed.【Results】The results showed that the surface morphologies of MAO coating on 6061 aluminum alloys were similar to the porous volcano-like microstructures.When the voltage was lower than 450 V,the thickness of the coatings increased with the increase of working voltage.At the same time,the number of crater-shaped discharge holes increased,the main phase of the coating wasβ?Al2 O3 and a small amount ofα?Al2 O3.After the working voltage was greater than 450 V,the number of crater-shaped discharge holes decreased,on the contrary,the diameter of the channels increased.When the working voltage increased to 500 V,the coating began to show micro-cracks,and the corrosion resistance first increased and then weakened.【Conclusion】When the working voltage was 450 V,resistance of discharge micro-pore in porous layer of the coatings Rp was 2.875×106Ω·cm2,and resistance of corrosion reaction charge transfer in matrix metal was 7.575×106Ω·cm2,which showed better corrosion resistance than other prepared coatings.