汽车修补涂装工艺一般由表面准备、涂底漆、刮腻子填平、喷中涂层、涂面漆等工序组成。
1.表面准备
日的是得到清洁、平滑的表面,以利于涂装的进行。在进行表面平整工序之前,首先应对原有旧漆层的涂料系统和大致状况进行辨认,以免出现涂装后效果不佳甚至需重喷涂的情况,此项工作应由有丰富实践经验的熟练技工担任。然后进行表面清洗处理,因为在喷涂表面有任何杂质污垢都会影响涂膜的耐久性和附着力,所以有效清洁被涂表面极为重要,一般首先用肥皂水或清洗剂将要修补部位及周围区域进行清洗,有时需将整个车身清洗,以除去灰尘及水溶性污垢,然后用溶剂清洗剂或中性的水基清洗剂进行脱脂清洗,去除修补部位上的油污,洗净后要用水冲洗干净,并用鹿皮或吸水毛巾擦干,再用低压压缩空气吹净残留水珠及缝隙、槽沟中的灰尘,接着对需修补的漆面进行湿打磨,一般用240#~320#水砂纸,由于大多数已损坏的旧涂层是不能仅靠重新涂装的方法使其性能恢复的,而且有时重新涂装还会加速旧涂层的恶化,所以在涂装前需要将损坏的旧涂层打磨去除。打磨时应判断旧涂层的附着情况,在对涂层边缘打磨时如果发现薄边没有裂开或碎掉,则可以保留这部分旧涂层。而有锈蚀或附着力不好的部分则需要清除干净,直至露出金属表面为止,以创造良好的基底和消除漆面上任何的瑕疵。打磨时要用大量清水冲洗,用湿海绵除去打磨残渣并用洗涤廃皮擦干。然后对打磨后裸露金属的部位做交接边缘使交接处平顺,达到用手指摸也感觉不到的程度。最后用200#汽油或乙醇擦拭，以确保被涂面完全清洁。
2.表面整平工艺
这是汽车修补涂裝的关键工序之一,它能起到消除被涂面缺陷,经加工后可获得平整表面和增强层间附着力的作用。它直接影响到涂装质量成本和工效。它是由刮腻子和磨平两道工序组成的。
(1)刮腻子是使用涂刮填平性好的中间涂料(膩子和二道浆)来消除被涂表面的凹陷、划伤等缺陷的工序,当凹陷深度在100µm以上时,使用刮涂腻子的方法来填平,深度在100µm以下时,用喷涂二道浆的方法来填平。
Putties commonly used in repair coating include sheet metal putty, unsaturated polyester putty and quick-drying putty. Although putty can improve the decorative appearance of the coated surface coating, it cannot improve the protective performance of the coating. Moreover, the putty has a high pigment content, lacks elasticity, and is easy to crack, resulting in damage to the coating. In addition, putting putty is a low-efficiency process , Labor-intensive processes, so attention should be paid to scraping putty as little as possible under the premise of ensuring quality requirements. When applying and scraping the putty, care should be taken to make the putty uniform, especially the two-component putty must be mixed evenly; do not repeatedly apply and scrape when applying and scraping, so as to prevent the curling and surface sealing from affecting the drying of the putty layer; For thick occasions, it should be applied and scraped several times. First, apply and scrape the thin layer, then fill the pit, and then scrape or scrape thinly. The dry "sugar heart" as well as blistering, cracking and other phenomena. After each layer of putty is dry, sanded and wiped clean, a layer of putty can be scraped off.
(2) The smoothing process is the process of smoothing the coated surface by dry or wet grinding, the purpose of which is to obtain a smooth surface and enhance the adhesion between the coatings. According to the operation method, it can be divided into manual smoothing, manual grinding with cork or hard rubber block behind the sandpaper for assistance, and grinding with a sander. According to the different types of lubricants used, it is divided into wet grinding and dry grinding, both of which use sandpaper to remove uneven traces on the coating film to obtain the required flat surface. In order to control and eliminate sandpaper marks and wear marks, finer grades of sandpaper should be gradually used during the coating process, such as 240#~320# water sandpaper for wet sanding before painting, and 360#~ 500# water sandpaper, the final smoothing process is better to use 600# water sandpaper for wet grinding.
