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Introduction to the reasons that affect the quality of automotive spray paint

05-10

Automotive spray painting is a technical work. In the past, automotive spray coatings were mainly colored paints (white, blue, black, red and other monochromatic colors and related multi-colors, etc.). Relatively speaking, the requirements for spraying repair paints were not high. However, with the rapid development of metallic glitter paints and pearlescent paints, the use of relatively rare light metallic glitter paints in the past has also increased. As automotive paint grades become more and more luxurious, the performance of automotive refinish paints continues to improve, and the requirements for painters have also increased. 的施工稳定性、色差等质量的控制都存在不同程度的难点,尤其是它的“视角闪色效应”(从正面、侧面观察其明度、色相以及彩度等的差异)上比深色漆要敏感得多。 For example, there are varying degrees of difficulty in controlling the quality of sprayed light-colored metallic paints , such as the construction stability and color difference, especially its "perspective flash effect" (observing its brightness, hue, and chroma from the front and sides). Difference) is much more sensitive than dark paint.

Therefore, when spraying light-colored metallic flash paint, the coating conditions and processes should be strictly controlled in accordance with the construction requirements of the automotive refinish paint used. 、施工工具,而且对施工环境(温度、湿度)的控制、冬夏季节稀释剂的选择以及喷枪的调旅等都必须认真对待,忽视任何一个环节都可能造成灾难性的后果。 In short, when spraying automotive paint, we must not only carefully select the materials and construction tools used, but also control the construction environment (temperature, humidity), the choice of thinners for winter and summer seasons, and the transfer of spray guns, etc., and we must ignore any one. Links can have disastrous consequences.

Generally speaking, the main factors affecting the quality of automotive paint spraying are as follows:

(1) Viscosity of automotive spray paints <br /> Viscosity is a measure of the interaction between liquid molecules and the ability to hinder relative movement between molecules. It can also be called the liquid flow resistance (internal friction). 、稀释剂及温度的变化对液体流动性都有影响。 Generally speaking, the thinness and thickness of the paint material actually refers to the size of its viscosity, and the changes of the solvent , diluent and temperature all affect the fluidity of the liquid. Also, it is the fluidity that determines the atomization quality of the paint, the fluidity on the component surface, and the type of spray equipment.

When preparing paint, strictly follow the technical requirements provided by the paint supplier, and dilute the paint to the appropriate viscosity with the diluent that is most suitable for the temperature and conditions of the repair beauty shop. Otherwise, if the viscosity is too high, the surface will be rough and uneven, causing defects such as pinholes and pores; if the viscosity is too low, it will cause hanging flow, loss of light, and make the paint film not full. Therefore, the viscosity of the vehicle body paint should be adjusted according to technical requirements, and the habit of testing with a viscometer should be developed.

The amount of diluent should be independent of temperature. When the temperature is higher, the actual viscosity of the diluted paint may be slightly lower, but when sprayed from the spray gun to the surface of the component, the diluent volatilizes quickly. As a result, the viscosity of the paint when it reaches the surface of the coated component is just right. On the contrary, when the room temperature is low, the viscosity of the diluted paint is higher, but the volatilization is slow, and the viscosity is just right when it reaches the surface of the component.

According to relevant regulations in China, the commonly used viscometers are Tu-1, Tu-4, and falling-ball viscometers. The unit of measurement is "s".


In actual production, the Tu 4 viscometer is widely used, and it can be used to determine various coating products with viscosity between 10 and 15 s. There are two types of Ford cups and Zahn cups used to test the viscosity of automotive paints abroad. The Ford cup No. 4 is commonly used. It is aluminum alloy or thick copper turned into a cylinder with a volume of 100ml, and the bottom of the cup is conical. Hole with a caliber of 4mm. The test principle and method are similar to the Tu-4 viscometer, but the temperature should be controlled to 20 ° C.

(2) Temperature control

喷涂和干燥时的温度对漆面的光洁影响很大,这里既指喷漆室的温度,也指构件的表面温度。 The temperature of automobile paint spraying and drying has a great influence on the finish of the paint surface. Here it refers to both the temperature of the spray booth and the surface temperature of the component. Spraying hot paint on cold components or spraying cold paint on hot components can impair fluidity. The thinner should also be selected according to the warm and cold weather.


(3) Use of spray gun

In order to achieve a smooth, smooth, uniform thickness and light-like mirror surface, in addition to the variety and quality of the coating and the underlying foundation of the component being sprayed, it is more important to have rich spraying experience and correct operating techniques. 喷涂操作前,操作人员必须掌握好最基本的喷枪调整和使用方法。 Before spray gun operation, the operator must master the most basic gun adjustment and use methods.

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