多种铝合金和钢铁材料兼顾的底涂工艺技术已成为新能源汽车轻量化车身制造的重点需求。在6061、7075铝合金和镀锌钢上开展了基于钛/锆复合体系的多种金属表面化学转化研究。通过硫酸铜点滴实验考察了H2TiF6浓度、H2ZrF6浓度及工艺参数对3种金属表面膜层耐蚀性的影响，并利用电化学测试方法对其膜层耐蚀性的优劣进行了验证；使用扫描电镜及能谱仪观察分析了转化膜表面形貌及元素构成。结果表明：当H2TiF6浓度在1.60～2.00 mL/L、H2ZrF6浓度在0.80～1.30 mL/L、转化时间在90～150 s、pH值在3.5～4.5、温度处于30～40 ℃之间时，3种金属材料经转化后，其耐蚀性较为良好。与空白样品对比，3种金属试样的Jcorr均有明显下降，且空白样品的Ecorr明显低于其他试样。EIS谱显示转化后的3种金属的膜层电阻Rct较空白样品的有明显增大。SEM形貌展示了不同时间下样品表面微观形貌的差异，在120 s时6061铝合金、7075铝合金、镀锌钢表面的微孔和裂缝明显更少。
The primer coating technology applicable to a variety of aluminum alloys and steel materials has become a key requirement for the manufacturing of lightweight body for new energy vehicles. In this paper, a study on chemical conversion of metal surfaces based on the titanium/zirconium composite system was carried out on 6061 and 7075 aluminum alloys and galvanized steel. The effects of H2TiF6 concentration, H2ZrF6 concentration and process parameters on the corrosion resistance of the coatings formed on the surfaces of the three metals were investigated through copper sulfate spot experiments, and the corrosion resistance of the coatings was verified by electrochemical testing. Moreover, the scanning electron microscope and the energy spectrometer were employed to observe and analyze the surface morphology and element composition of the conversion coatings. Results showed that after a conversion treatment under the conditions that the H2TiF6 concentration was 1.60～2.00 mL/L, the H2ZrF6 concentration was 0.80～1.30 mL/L, the conversion time was 90 ～ 150 s, the pH value was 3.5 ～ 4.5, and the temperature was 30～40 ℃, these three kinds of metal materials possessed good corrosion resistance. The Jcorr of three metal materials decreased significantly in comparison with that of the blank sample, and the Ecorr of the blank sample was significantly lower than that of the other samples. In addition, the EIS spectrum showed that the film resistance Rct of the three metal materials treated with chemical conversion was significantly higher than that of the blank sample. The differences in the surface microstructure of the samples at different times was observed by SEM, and there were significantly fewer micropores and cracks on the surfaces of 6061 and 7075 aluminum alloys and galvanized steel after a treatment for 120 s.
