(1. 四川輕化工大學(xué) 材料科學(xué)與工程學(xué)院，自貢 643000；
2. 中國科學(xué)院 海洋新材料與應(yīng)用技術(shù)重點實驗室，寧波 315201)
摘 要: 為精確量化和評價微弧氧化(MAO)涂層的孔隙率，在硅酸鹽電解液中通過恒壓MAO方法于AZ31B鎂合金表面制備氧化物涂層。利用線性極化、電化學(xué)交流阻抗譜(EIS)和Tafel曲線分別計算涂層的極化電阻并考察其腐蝕防護性能，重點采用Image-J圖像法和兩種極化電阻比值法評價了涂層孔隙率，提出了適合MAO涂層孔隙率的評價方法。結(jié)果表明：當氧化電壓由260 V升至290 V時，MAO樣品的自腐蝕電流密度由2.8 μA/cm2增加至5.6 μA/cm2。結(jié)合線性極化電阻和EIS擬合結(jié)果，證實涂層腐蝕防護性能隨氧化電壓的升高而降低。同時，Image-J圖像法計算的表面孔隙率由10.14%增加至11.48%，線性極化電阻計算的通孔孔隙率由3.51%增加至7.08%，表明涂層腐蝕防護性能與其孔隙率呈負相關(guān)，即隨孔隙率增加而降低。與電化學(xué)交流阻抗譜或Tafel曲線所得極化電阻比值法相比，簡單的線性極化電阻比值法更適合量化MAO涂層的通孔孔隙率，而Image-J圖像法適合通過MAO涂層的表面SEM像量化表面孔隙率及孔徑大小的分布情況。
關(guān)鍵字: 鎂合金；微弧氧化；孔隙率；極化電阻；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
