Ti-48Al-2Cr-2Nb钝化膜的电化学性能及形成机理

Electrochemical Properties and Formation Mechanism of Ti-48Al-2Cr-2Nb Passive Film

探究Ti-48Al-2Cr-2Nb合金钝化膜的耐腐蚀性和形成机理对提高电解加工过程中的抗杂散腐蚀具有重要意义。通过极化曲线确定了Ti-48Al-2Cr-2Nb合金的钝化电位,采用X射线光电子能谱确定了钝化膜的成分与结构,并运用电化学阻抗谱和Mott-Schottky理论分析了钝化膜的电化学性能。结果表明,Ti-48Al-2Cr-2Nb合金在NaNO_(3)电解液中钝化电位区间为0.079~1.896V,钝化膜主要成分为Al_(2)O_(3)、TiO_(2)及少量的Nb_(2)O_(5),呈双层多孔结构,具有良好的耐腐蚀性。钝化膜具有n型半导体特性,载流子密度随钝化电位的增加而降低。最后,构建了钝化膜形成示意图,揭示了Ti-48Al-2Cr-2Nb合金钝化膜的形成机理与成相膜理论相符,以半球体模型延展并形成独立的相。

It is important to investigate the corrosion resistance and formation mechanism of passivefilm of Ti-48Al-2Cr-2Nb alloy to improve the resistance to stray corrosion during electrolytic machining.The passive potential of Ti-48Al-2Cr-2Nb alloy was determined by polarization curves,the composition and structure of the passivefilm were determined by X-ray photoelectron spectroscopy,while the electrochemical properties of the passivefilm were analyzed using electrochemical impedance spectroscopy and Mott-Schottky theory.The results showed that the passive potential interval of Ti-48Al-2Cr-2Nb alloy in NaNO_(3) electrolyte was 0.079~1.896 V,and the main components of the passivefilm were Al_(2)O_(3) and TiO_(2) and a small amount of Nb_(2)O_(5),which was a bilayered porous structure with good corrosion resistance.The passivefilm had n-type semiconductor properties,and the carrier density decreases with the increase of passive potential.Finally,the schematic diagram of the passive film was constructed.The formation mechanism of passivefilm of Ti-48Al-2Cr-2Nb alloy was consistent with the theory of phase-formingfilm,which extended and formed separate phases in a hemispherical model.