高低电压下不同厚度微弧氧化膜抗蚀电化学响应对比研究  

Comparative Study on Anti-corrosion Electrochemical Response of Micro-arc Oxidation Coatings with Different Thicknesses under High and Low Voltage

作　　者：孙乐[1] 马颖[1] 安凌云 王兴平 高唯[2] SUN Le;MA Ying;AN Ling-yun;WANG Xing-ping;GAO Wei(Province-ministry Co-constructed State Key Laboratory of Advanced Processing and Recycling of Non-ferrous Metals,Lanzhou University of Technology,Lanzhou 730050,China;Faculty of Engineering,The University of Auckland,Auckland 1142,New Zealand)

机构地区：[1]兰州理工大学省部共建有色金属先进加工与再利用国家重点实验室,兰州730050 [2]奥克兰大学工学院,新西兰奥克兰1142

出　　处：《表面技术》2021年第1期366-374,共9页Surface Technology

基　　金：甘肃省创新研究群体计划(1111RJDA011)。

摘　　要：目的对比研究具有不同厚度的微弧氧化膜的抗蚀电化学响应。方法通过调整电压,在硅酸盐电解液体系中,于AZ91D镁合金表面制备具有不同厚度的微弧氧化膜层。利用SEM、EPMA和XRD研究膜层的微观形貌、元素及物相组成,进而采用循环伏安(CV)法、动电位极化曲线和电化学阻抗谱(EIS),对比研究该膜层的抗蚀电化学响应。结果 AZ91D镁合金经微弧氧化处理后,其抗蚀性得以显著提高,但不同厚度的膜层的抗蚀电化学响应不同。相比低电压下制备的薄膜,高电压下制备的厚膜的抗蚀物相含量高,CV曲线环面积和腐蚀电流密度均降低了约1个数量级,线性极化电阻增大了约3.7倍,且其阻抗模值更高,膜层抗蚀性更优。两膜层的腐蚀失效过程不同。厚膜的腐蚀过程主要经历了2个阶段:腐蚀介质逐渐渗入膜层和腐蚀介质渗透至膜基界面侵蚀基体。薄膜的腐蚀过程经历了3个阶段:腐蚀介质逐渐渗入膜层、腐蚀介质渗透至膜基界面侵蚀基体和膜层完全失效。结论厚膜呈现出较弱的腐蚀倾向和优异的抗蚀性能,三种电化学测试的结果都能较好地相互印证,但在揭示膜层的腐蚀过程和腐蚀机制时各自的深入程度不同。The aims is to study the anti-corrosion electrochemical responses of micro-arc oxidation(MAO)coatings with different thicknesses contrastively.AZ91D magnesium alloys were treated in silicate-containing electrolyte by adjusting the voltage in order to obtain MAO coatings with different thicknesses,the microstructure,element and phase composition of these coatings were studied by using SEM,EPMA and XRD,respectively.And the anti-corrosion electrochemical responses of the coatings were studied contrastively by cyclic voltammetry(CV),potentiodynamic polarization test and electrochemical impedance spectroscopy(EIS).Anti-corrosion property of AZ91D magnesium alloys is significantly improved after MAO treatment,and the anti-corrosion electrochemical responses of the coatings with different thicknesses vary.Compared with the thin coating prepared under low voltage,the closed ring area surrounded by the CV curve and the corrosion current density of the thick coating prepared under high voltage both reduce about one order of magnitude,and its linear polarization resistance increases approximately 3.7 times.Meanwhile,its impedance modulus is higher and thus it exhibits more superior anti-corrosion performance.At the same time,the corrosion processes of two kinds of coatings are different,which can be divided into two stages for the thick coating,namely,the corrosive medium gradually penetrates into the coating,and then down to the interface between the coating and the substrate,eroding the substrate.While the deterioration of the thin coating mainly experiences three stages:the corrosive medium gradually infiltrates into the coating and penetrates through the coating/substrate interface,then corrodes the substrate,and finally the coating completely fails.In conclusion,the thick MAO coating has weak corrosion tendency and excellent anti-corrosion property,which is supported by the above three electrochemical testing results that reveal the corrosion process and mechanism of the thick coating with different degree respectively

关 键 词：AZ91D镁合金 微弧氧化 膜厚 抗蚀性 循环伏安 动电位极化曲线 电化学阻抗谱 电化学响应 

分 类 号：TG174.4[金属学及工艺—金属表面处理]