金属锆醇盐对钛合金表面溶胶−凝胶转化膜结构及漆层结合力的影响

Effect of zirconium alkoxide on structure of sol-gel conversion coating and adhesion of primer thereon

采用有机硅烷和金属锆醇盐为主成分、无水乙醇为溶剂,在TC4钛合金表面制备了溶胶−凝胶转化膜。采用扫描电镜(SEM)、能谱(EDS)、辉光放电质谱(GDMS)、X射线光电子能谱(XPS)等技术分析了金属锆醇盐含量对转化膜表面微观形貌和成分,以及纵深方向元素分布和氧元素价态的影响。通过电化学阻抗谱(EIS)分析了转化膜的电化学特性和结构特点。最后通过长时间湿热试验研究了金属锆醇盐含量对后续有机漆层结合力的影响。结果表明,制备的溶胶−凝胶转化膜分成有机层和无机层两部分,其中无机层主要是由Ti─O─Zr/Si共价键结构组成,有机层主要由硅烷的有机碳链交联形成。当金属锆醇盐含量为2000 mg/kg时,转化膜具有最佳的结构完整性,能够保证钛合金表面有机底漆优异的结合力和耐久性。

A conversion coating was formed on the surface of TC4 titanium alloy by sol–gel method in a solution comprising organic silane and zirconium alkoxide as main components with ethanol as solvent.The surface morphology and composition,and element distribution and valence state of oxygen along the depth direction of coating were analyzed by scanning electron microscopy(SEM),energy-dispersive spectroscopy(EDS),glow discharge mass spectrometry(GDMS),and X-ray photoelectron spectroscopy(XPS).The electrochemical properties and structure of the conversion coating were examined by electrochemical impedance spectroscopy(EIS).The effect of zirconium alkoxide content on the adhesion of organic primer coat was studied by long-term damp-heat test.The results showed that the sol–gel conversion coating consisted of an inorganic layer,which was mainly composed of covalently bonded Ti─O─Zr/Si structure,and an organic layer,which was formed by the crosslinking reaction of carbon chains attached to the silane.The sol–gel conversion coating obtained with 2000 mg/kg of zirconium alkoxide featured the best structure integrity,and the primer sprayed on it had excellent adhesion and durability.