铝合金表面有色钛/锆转化膜的成膜机理及性能

Formation Mechanism and Properties of Colored Ti/Zr-Based Conversion Coating on Aluminum Alloy

为了解决工业生产中钛/锆转化膜无色的问题,通过向含钛/锆的处理液中加入单宁酸及成膜促进剂,在铝合金表面制备了有色钛/锆转化膜.采用X射线能谱仪、扫描电镜、傅里叶变换红外光谱仪、X射线衍射仪、X射线光电子能谱仪和电化学工作站对转化膜的形成过程、形貌、组织结构、耐蚀性等进行了分析.结果表明:在铝合金表面成功制备出了金黄色、耐蚀性优异的转化膜,其主要成分是Na3AlF6,其次是单宁酸水解产物的金属络合物以及少量Al2O3.3H2O、TiO2等;膜的形成可分为Na3AlF6晶体成核、生长和金属络合物的沉积3个阶段;转化膜的腐蚀电流密度由基体的5.894μA/cm2下降到0.283μA/cm2,耐蚀性明显提高.

In order to overcome the colorlessness of Ti/Zr conversion coatings applied in industry,a colored Ti/Zr conversion coating was prepared on the surface of aluminum alloy by adding tannic acid and film-forming accelerator in the treatment solution containing titanium and zirconium ions.Then,the growth process,morphology,microstructure and corrosion resistance of the coating were characterized and analyzed by means of EDS,SEM,FT-IR,XRD,XPS and by using an electrochemical workstation.The results show that golden conversion coatings with strong corrosion resistance can be successfully prepared on the surface of aluminum alloy,that the coating mainly contains Na3AlF6,followed with the metal complexes of tannic acid hydrolysate and a small amount of Al2O3·3H2O and TiO2,that the formation of the golden coating undergoes a process consisting of nucleation,crystal growth and metal complex formation,and that the corrosion resistance of the coating greatly improves because there occurs a sharp decrease in corrosion current density from 5.894 μA/cm2 to 0.283 μA/cm2.