钼酸盐对航空铝合金表面恒电位沉积聚吡咯膜耐蚀性的影响

Effect of molybdate on corrosion resistance of polypyrrole coating prepared by potentiostatic electrodeposition on aeronautical aluminum alloy surface

采用恒电位法在2024铝合金表面电沉积含钼酸盐的聚吡咯薄膜(标记为PPy–MoO4^2-)。采用场发射扫描电镜、能谱仪、X射线光电子能谱仪、傅里叶红外光谱仪和接触角测量仪分析了PPy– MoO4^2-膜的微观形貌、结构和疏水性,并通过塔菲尔(Tafel)曲线测试、电化学阻抗谱(EIS)测试和盐水浸泡试验对比了PPy–MoO4^2-膜、PPy膜和2024铝合金的耐蚀性。结果表明,PPy– MoO4^2-膜内存在Mo,且发现MoO4^2-的伸缩振动吸收峰,证明MoO4^2-有参与电沉积。PPy– MoO4^2-膜表面比PPy薄膜更致密、平整,疏水性更佳。PPy–MoO4^2-膜的耐蚀性优于PPy膜,对铝合金基体起到阳极保护的作用。

A polypyrrole coating containing molybdate(coded as PPy-MoO4^2-)was electrodeposited on the surface of 2024 aluminum alloy under constant potential.The microscopic morphology and structure,as well as hydrophobicity of the PPy– MoO4^2-coating were analyzed using field-emission electron scanning microscope,energy-dispersive spectrometer,X-ray photoelectron spectrometer,Fourier-transform infrared spectrometer,and contact angle meter.The corrosion resistance of PPy–MoO4^2-coating,PPy coating,and 2024 aluminum alloy was compared based on Tafel curves and electrochemical impendence spectra.The results showed that there exists Mo in PPy– MoO4^2-coating and the absorption peak of stretching vibration from MoO4^2-was found,identifying the participation of MoO4^2-in electrodeposition.The PPy– MoO4^2-coating was not only more compacter and smoother,but also had better hydrophobicity as compared with the PPy coating.The PPy– MoO4^2-coating plays the role of anodic protection to aluminum alloy substrate with a better corrosion resistance than the PPy coating.