TA15合金微弧氧化陶瓷涂层制备与电偶腐蚀性能

Preparation and Galvanic Corrosion Resistance of Microarc Oxidation Ceramic Coatings on TA15 Alloy

目的改善TA15合金(Ti6Al2Zr1Mo1V)与异种金属间接触时产生的电偶腐蚀性能。方法采用微弧氧化(Microarc oxidation,MAO)方法在硅酸盐电解液中,于钛合金表面制备TiO2基陶瓷涂层。采用XRD、SEM和EDS等方法,表征涂层的物相成分、组织结构及元素分布,用极化曲线、电化学阻抗谱和电偶腐蚀等测试涂层的耐腐蚀性能。结果微弧氧化涂层由内外两层组成,内层致密,外层疏松多微孔,且内层与基体的结合呈现凹凸界面,出现“局部过生长”现象。涂层以金红石和锐钛矿TiO2相为主。与基体合金相比,陶瓷涂层的自腐蚀电位提高了0.672V;随氧化时间的延长,涂层厚度增加,内层变得更加致密,涂层的自腐蚀电位提高。涂层内层的阻抗模值,随氧化时间的增加而增大,分别为1.16×10^6Ω·cm^2(10min)、1.2×10^6Ω·cm^2(30min)和3.8×10^6Ω·cm^2(50min)。在3.5%NaCl溶液中进行电偶腐蚀试验15天后,30CrMnSiA钢/TA15合金微弧氧化涂层对偶件的平均电偶腐蚀速度,明显低于30CrMnSiA钢与TA15合金、巴氏合金、铝青铜偶接时的腐蚀速度。结论微弧氧化致密阻挡层具有良好的阻隔特性,降低了电偶腐蚀敏感度,有效缓解了电偶腐蚀的发生。

The work aims to alleviate the galvanic corrosion between TA15 alloy (Ti6Al2Zr1Mo1V) and dissimilar metals caused by contact.TiO2 ceramic coating was fabricated on the surface of titanium alloy by microarc oxidation (MAO) method in silicate based electrolyte.The phase composition,microstructure and distribution of element of the coatings were characterized by characterization methods such as XRD,SEM and EDS,and the corrosion resistance was investigated by polarization curves, electrochemical impedance spectrum (EIS) and galvanic corrosion.The MAO coating was composed of inner layer and outer layer.The inner layer was dense,while the outer layer was loose and microporous.The bonding of the inner layer and matrix showed a concave and convex interface,and the phenomenon of ‘local over-growth’ appeared in some local regions.The coating mainly consisted of rutile and anatase TiO2.Compared with matrix alloy,the self-corrosion potential of the coating was increased by 0.672 V.Meanwhile,with the oxidation time increasing,the coating thickness increased and the inner layer became denser,which improved the self-corrosion potential of the coating.As the increase of oxidation time,the impedance of the inner layer increased,which was 1.16×10^6 Ω·cm^2 (10 min),1.2×10^6 Ω·cm^2 (30 min),and 3.8×10^6 Ω·cm^2 (50 min),respectively.After galvanic corrosion testing for 15 days in 3.5wt.% NaCl solution,the average galvanic corrosion rate of steel/MAO coating on TA15 alloy was significantly lower than the corrosion rate of 30CrMnSiA steel coupled with TA15 alloy,babbitt and albronze. The excellent dense barrier inner layer of the MAO coatings has good blocking features and reduces the galvanic corrosion sensitivity, thus effectively alleviating the occurrence of galvanic corrosion.