(1. 四川轻化工大学 材料科学与工程学院，自贡 643000；
2. 中国科学院 海洋新材料与应用技术重点实验室，宁波 315201)
摘 要: 为精确量化和评价微弧氧化(MAO)涂层的孔隙率，在硅酸盐电解液中通过恒压MAO方法于AZ31B镁合金表面制备氧化物涂层。利用线性极化、电化学交流阻抗谱(EIS)和Tafel曲线分别计算涂层的极化电阻并考察其腐蚀防护性能，重点采用Image-J图像法和两种极化电阻比值法评价了涂层孔隙率，提出了适合MAO涂层孔隙率的评价方法。结果表明：当氧化电压由260 V升至290 V时，MAO样品的自腐蚀电流密度由2.8 μA/cm2增加至5.6 μA/cm2。结合线性极化电阻和EIS拟合结果，证实涂层腐蚀防护性能随氧化电压的升高而降低。同时，Image-J图像法计算的表面孔隙率由10.14%增加至11.48%，线性极化电阻计算的通孔孔隙率由3.51%增加至7.08%，表明涂层腐蚀防护性能与其孔隙率呈负相关，即随孔隙率增加而降低。与电化学交流阻抗谱或Tafel曲线所得极化电阻比值法相比，简单的线性极化电阻比值法更适合量化MAO涂层的通孔孔隙率，而Image-J图像法适合通过MAO涂层的表面SEM像量化表面孔隙率及孔径大小的分布情况。
关键字: 镁合金；微弧氧化；孔隙率；极化电阻；Image-J
（1. School of Materials Science and Engineering, Sichuan University of Science and Engineering, Zigong 643000, China;
2. Key Laboratory of Marine Materials and Related Technologies, Ningbo Institute of Materials Technology and Engineering, Chinese Academy of Sciences, Ningbo 315201, China）
Abstract:To accurately determine and evaluate the porosity of micro-arc oxidation (MAO) coating, an MAO coating was fabricated on AZ31B Mg alloy via a constant voltage mode in a Na2SiO3 base aqueous solution. The polarization resistance and anti-corrosion property of the coatings were investigated by linear polarization resistance, electrochemical impedance spectroscopy(EIS) and Tafel polarization curve measurements, respectively. The focus was on the calculation and evaluation of the porosity by Image-J and two optimized polarization resistance ratio methods, and presenting an assessment method for the porosity of MAO coatings. The corrosion current density (Jcorr) of the MAO coated Mg alloy increases from 2.8 μA/cm2 to 5.6 μA/cm2 with the oxidation voltage increasing from 260 V to 290 V. Combined with the results of linear polarization resistance and EIS fitting, the corrosion protection performance of the coating decreases with increasing the oxidation voltage. Additionally, the surface porosity calculated by Image-J method increases from 10.14% to 11.48%, and the through-hole porosity calculated by linear polarization resistance method increases from 3.51% to 7.08%, implying that the anti-corrosion of the coating is negatively correlated with its porosity, i.e. it decreases with the increase of porosity. Among several methods for polarization resistance and porosity assessment methods, the linear polarization resistance measurement is more suitable for determining the through-hole porosity of the MAO coating, while the Image-J method can be used to quantify surface porosity, the distribution of pore size by the SEM image of an MAO coating.
Key words: magnesium alloy; micro-arc oxidation; porosity; polarization resistance; Image-J
