染色和封孔对铝阳极氧化膜结构和耐蚀性的影响

目前,染色和封孔对铝阳极氧化膜的结构和耐蚀性的影响尚不清楚,且有机染色工艺还不够好。采用200 g/L H2SO4电解液在高纯铝表面制备了综合性能良好的阳极氧化膜,通过含芳香烃的有机偶氮染色剂DLM2203和DLM2707对铝阳极氧化膜进行染色处理,用沸水对染色膜进行封孔处理。采用扫描电镜(SEM)、X射线衍射仪(XRD)、红外光谱仪等分析铝阳极氧化膜及染色膜的表面形貌和相组成,并采用动电位极化曲线、电化学阻抗谱等分析铝阳极氧化膜和染色膜的耐蚀性能。结果表明:铝阳极氧化膜染色均匀,表面平整;染色膜经过沸水封闭处理后,其外观颜色变浅;铝阳极氧化膜经染色处理后,厚度和显微硬度都略有增大;沸水封闭导致染色膜厚度略有增大,而显微硬度减小;铝阳极氧化膜的部分孔洞可被DLM2203染色剂充分吸附而成功染色;DLM2707有机染色剂对铝阳极氧化膜有一定的腐蚀作用;铝阳极氧化膜和2种染色膜的相组成相同;偶氮染料分子可以吸附在铝阳极氧化膜的多孔结构内与表面上;染色膜的腐蚀电流密度相对于高纯铝降低了4个数量级,耐蚀性能较好;铝阳极氧化膜与染色膜的阻抗值均处在同一数量级上,耐腐蚀性能基本相近。

Influences of Coloration and Sealing on Structure and Corrosion Resistance of Anodic Films on Pure Aluminum Sheets

Anodic films on pure aluminum sheets were prepared in 200 g/L sulphuric acid electrolyte.Anodic films were dyed with DLM2203 and DLM2707 organic dyes and then sealed by boiling water.The morphology and structure of anodic films were studied using scanning electron microscope (SEM),X-ray diffraction(XRD) and infrared spectrum.The corrosion resistances of anodic films and coloration films were studied using potentiodynamic polarization and electrochemical impedance spectroscopy relatively.Results showed that anodic films on pure aluminum sheets were uniform and smooth after coloration process.The coloration films after sealing treatment in boiling water faded slightly.The coloration films had slightly larger thickness and microhardness than anodic films on pure aluminum sheets.After boiling water sealing,the thickness of coloration films increased while the microhardness of coloration films decreased slightly.Some pores of anodic films were fully filled by DLM2203 dyeing agents and the film surface became yellow.The DLM2707 dyeing agents had corrosion effect on anodic films.The phase structures of anodic films and coloration films were identical.The azo dyes with the active nitrogen-nitrogen double bond could be absorbed in the anodic films.The corrosion current density of coloration films was lower than that of pure aluminum sheets by four orders of magnitude.The electrochemical impedance spectra modulus of anodic films and DLM coloration films were in the same order of magnitude,and their corrosion resistances were similar.