Automotive topcoat layer scratch through the primer coating process

在进行轿车油漆护理时，如果经检查认定面漆层已被刮透，但未伤及底层涂漆其护理喷涂工艺如下：

1、打磨清洗

在底层涂漆附着完好的情况下，对中涂层及面漆层的刮伤部分进行打磨清洗，并加以修整损伤部位的边缘，使其边缘不见有损伤的涂层、附着力都很良好的部位出现为止。

2、表面处理，确保处理质量

在除去刮伤部分的中涂层及面漆层之后，打磨平整使之光滑，并对边缘部分进行适当的扩大面积进行表面处理。用专用清洗剂去除此表面的油污、石蜡及其他异物，并使之干燥。若此部位的面积较大，可用远红外灯进行烘烤，使待涂装的表面达到平整、光滑、干净，达到待涂装的表面质量标准的要求。

3、表面处理的注意事项

当使用压缩空气来吹去待涂装表面的粉尘进，则空气压缩机需要带有油水分离器，使吹出的压缩空气中不应带有油份和水汽。已进行表面处理后待涂装的表面，不允许用手去触摸，往往使手皮肤上的油粘污的已清洁的表面，否则会导致涂层附着不良，影响喷涂质量。

若表面处理工作质量不好，就会产生如下涂层弊病：

（1）当带有强溶剂的涂料喷涂到局部氧化的表面上，或表面处理不很干净，或表面含有石蜡等物质存时，均可能使涂层起皱。

（2）当喷涂前，已处理好的表面，或未能有效清洁处理好的表面，落上了碎屑或小颗粒异物。涂装后，会导致涂层表面凸凹不平，易见碎屑等弊病出现。

（3）若打磨后的表面未能有效清理，尚有磨料颗粒存在，则会造成涂层呈现出鱼眼状表面。

（4）当喷涂表面不当，车身表面未有效干燥，有的部位残留有水份，则使涂装后的涂层表面出现涂膜含水珠。

（5）若表面处理不有效，残留有尘土、水汽或其他异物浸入而使涂层分离产生起泡。

（6）由于表面处理不有效，残留异物浸入而使涂层分离状况不同，产生细小针状泡。

4、中涂层喷涂施工

在前面处理好的干燥而清洁的待涂表面上涂装底涂层，待烘干燥后即可。按要求选定好中涂层涂料施工条件并进行中涂层喷涂施工。以TP—37高固体分环氧聚酯型氨基汽车中涂层漆为例，制定其护理涂装工艺如下：

（1）施工工艺参数。施工粘度为（26±3）s/25℃（涂—4）手工操作。稀释率为（20±5）WT%；雾化压力为30~50N/c㎡（枪口压）；雾化幅为25cm；涂装距离为25cm；重涂幅为2/3；吐出量为300~500mL/min。流平时间为10~15min（常温）；干燥温度为140℃；干燥时间为20min；干燥膜厚为（35±5）um（一次性成膜）。

（2）遮盖好不喷涂的部位。

（3）使用设备：在室内空气喷涂法使用的主要设备有空气压缩机、油水分离器、压力表及控制器、压力输送管、涂料输送管、涂料贮存罐及喷枪枪等。工作原理如图所示：

汽车喷涂，特别是在维修护理喷涂中，常用有虹吸式杯的喷枪进行喷涂作业。这种喷枪的板机既控制空气，又控制涂料。这种喷枪，都有一套完整的配套用的喷嘴、喷针和喷杯，以适应喷涂各种涂料和不同的喷涂量。一般维修护理厂均有多套喷枪，分别用来喷涂底漆，中涂层漆及面漆，以更好地保质保量完成喷涂。

（4）中涂层漆烘干。若修补面积不大，可采用室温自然干燥，但时间较长；一般常用远红外线干燥煤或远红外线干燥箱（反射式）进行局部干燥。

（5）中涂层漆膜打磨清洁。当干燥后的中涂层漆膜进行打磨时，用320号的水磨砂纸修补的中涂面漆进行表面打磨，同样打磨到用手触摸无粗糙感为止，并用水冲洗干净，将水擦干，晾干或用压缩空气吹干，更好还是用远红外线灯箱烘干。

5、喷涂面漆

将已选定好的面漆，按施工条件的要求，调配到规定的工艺条件允许范围内，然后进行喷涂。每次喷涂之间，需要有涂膜足够的流平时间，若选用的面漆是TM—01各色氨基烘干汽车面漆，则涂料是流平时间为5~8min。为了保证面漆层的要求厚度，每次重叠喷涂面漆之间的涂膜流平时间是5~8min，第一次喷涂完了之后的流平时间是10~15min，这都是以喷涂室的室温在25℃条件下的工艺参数。当室温较低时，时间则要适当长些，以涂料的流平状况为准。

TM—01氨基烘干汽车面漆的施工条件：

（1）使用前需要将面漆搅拌均匀，并用绢布或丝棉布过滤。

(2) During construction, manual spraying or electrostatic spraying is the main method. Thinning solvents require the use of matching topcoat thinners.

(3) When spraying by hand, the viscosity of the paint is 22~24/s25℃, measured by Tu-4 viscometer.

(4) When the topcoat is painted by hand, in order to ensure the thickness of the coating film, it should be sprayed twice, and the leveling time between layers is 5-8 minutes; the leveling time after the first spraying is 10-15 minutes.

(5) The matching primer for this product is 8603 cathodic electrophoresis primer, and the intermediate paint is SM-01 medium coating paint. The total thickness of the car body coating is 80~110um. Generally, two paints and one varnish are used to form the entire topcoat thickness of the car. The thickness of the topcoat layer is generally 50~60um. The thickness of the first topcoat spraying is 30~40um, and after leveling for 10~15min, it needs to be dried.

6. Drying of the first top coat

Because it is maintenance coating drying, the drying principle is the same as that of car manufacturing. In order to comprehensively consider economic benefits and quality, the drying equipment used cannot be exactly the same. When the area of ​​maintenance coating is small, it is impossible to bake in the drying room of the whole vehicle, because the energy waste is too large, so special far-infrared baking lamps or ovens are generally used for partial drying. The temperature and time of baking depends on the actual situation on site, but it needs to meet the quality requirements of baking. The cotton ball method can be used to determine whether the surface of the paint film is actually dry. After the actual dryness, the next construction can be carried out.

7. Polishing of the first top coat

Use No. 320 sandpaper to polish the topcoat surface to make the surface of the second topcoat coating smooth, and use a rag and compressed air to blow and grind it clean. Finally, wipe the surface effectively with a sticky rag, and wait for the second topcoat to be sprayed.

8. Spray the second top coat

Because the material of the second topcoat has not changed, its process method and construction requirements are the same as those of the first topcoat. Coating film thickness 30~40um. The final leveling time is 10~15min.

9. Dry the second topcoat

The second topcoat drying process is the same as the first topcoat baking process. The construction requirements and environmental conditions have not changed, but the total thickness of the topcoat layer has been increased.

10. Polishing of the second top coat

For this topcoat grinding, special attention should be paid to the grinding quality, because it is the final grinding process that directly affects the surface quality of the coating. Lightly wet sand with 500 to 600 grit sandpaper to eliminate coating defects, then dry.

11. Sprayed varnish layer

Spray a layer of amino varnish on the sanded and dried car. Some repair shops combine this process into the second topcoat spraying. The specific method is to add the finish varnish before the construction of the original topcoat, and the addition amount should not exceed 20%, and then add a thinner and stir well to increase its gloss. Its viscosity should be appropriately thinner, and it should be used after filtering. This process can reduce one process, but in terms of the coating quality of the surface coating, it will definitely not be the same. If the partial coating repair has little application value, the film structure of the original car coating should also be referred to. If the original car coating has a finish layer, it should be carried out according to this process.

(1) Construction of varnish. Construction conditions: Take the varnish KH-24 as an example, use the special thinner KH-24; the dilution rate is 14%~16%; the dilution viscosity is 24~25s/25°C (coating -4); the construction solid content mass fraction is 46% ; Stability after standing for 48 hours, easy to restore by stirring gently.

Coating method: spraying times 5~6 times, target thickness 35~40um. Leveling between each time 3~5min; last leveling time 7~10min.

(2) Drying of varnish. Drying conditions, under the condition of 140 ℃, dry for 30 minutes; if the holding type is used in the drying room, the drying time is 20 minutes. If it is dry in a small area locally, use a far-infrared heater to bake until the time is actually dry.

12. Waxing and polishing

The purpose of waxing and polishing is to enhance the luster and protection of the surface coating. If you polish and wax frequently, the coating will always be bright and water-resistant, which can prolong the service life of the coating.

The construction procedure of waxing and polishing is to first soak the sand wax (polishing agent) with cotton cloth, woolen wool, sponge, etc., polish it, and then wipe it clean. Sand wax is used for polishing various coatings and smoothing uneven surfaces, which can eliminate the disadvantages of orange peel, pollution, whitening, and coarse grains of the coating.

The composition of sand wax is mostly an immobile wax slurry substance. When selecting abrasives, it should not contain coarse particles that wear and polish the surface, and the coating should not be colored during use. After polishing with sand wax, the surface of the coating is basically water-resistant. The quality of the glazing wax mainly depends on the performance of the wax. The new type of glazing wax is a waxy emulsion. Due to the finer dispersed particles and the presence of emulsifiers or a small amount of silicone components, it can help disperse and decontaminate during polishing. Therefore, a brighter effect can be obtained.