汽车内铝饰条典型外观缺陷分析

Typical Appearance Defects Analysis of Aluminium Trim in Vehicle Door

目的分析汽车内铝饰条手感漆脱落、白印和边缘腐蚀等典型外观缺陷产生的原因,从而避免此类问题的产生。方法用光学显微镜和电子显微镜对漆层、金属基体以及涂层和金属基体之间的间隙进行观察和测量,通过对生产工艺过程进行模拟,研究不同工艺参数对涂层外观及性能的影响。结果清漆160℃下烘烤30 min,手感漆的附着力良好,烘烤时间为60 min,手感漆容易脱落。通过对铝饰条生产工艺过程的模拟,发现静置时间分别为2 h、2 d,在热水擦拭和温度交变的情况下,铝饰条会产生与问题零件形态一致的白色印记,并且该印记烘烤(70℃/5 min)后消失。发生腐蚀的问题零件,铝饰条和镀铬饰条之间存在的间隙为135μm,边缘粗糙,拉丝深度为7.4μm,并且清漆和铝基体之间的间隙较大;未发生腐蚀的合格零件,铝饰条和镀铬饰条之间存在的间隙为17μm,边缘光滑,拉丝深度为2.2μm,并且清漆和铝基体之间的间隙较小。结论清漆烘烤时间过长,会导致手感漆在清漆上的附着力变差。铝饰条上的白色印记可能是由静置时间过短、存在热水擦拭和温度交变的情况下综合所致。铝饰条和镀铬饰条之间存在较大的间隙,铝饰条切边粗糙,拉丝深度较深,这会导致车门内铝饰条发生边缘腐蚀。

The work aims to avoid such defects of aluminum trim indoor as handfeel paint peeling off, white prints and edge corrosion by analyzing the causes. Optical microscope and SEM were used to observe and measure the paint, base metal, and gap between the paint and the metal. The effects of different process parameters on the coating appearance and performance were studied based on production process simulation. The handfeel paint had a good adhesion when the varnish was baked at 160 ℃ for 30 min, and peeled off easily when the varnish was baked for 60 min. By simulating the production process, we found that white prints in same morphology of those present in failure parts were present in aluminum trim provided with the standing time of 2 h, 2 d, hot water wiping and temperature alternating, and the white prints disappeared after being baked at 75 ℃ for 5 min. For corroded failure parts, the gap between Al trim and chromed trim was 135 μm, the edges were rough, wiredrawing depth was 7.4 μm and the gap between the paint and Al substrate was large. However, for uncorroded qualified parts, the gap between Al trim and chromed trim was 17 μm, the edge was smooth, the wiredrawing depth was 2.2 μm, and the gap between the paint and the Al substrate was small. Long-term baking of the varnish will lead to a poor adhesion of the handfeel paint to the varnish. The white print may be jointly caused by short standing time, hot water wiping and temperature alternating. The edge corrosion of the Al trim may be caused by large gap between the Al trim and chrome trim, rough edge and deep wiredrawing.