Cathodic electrophoresis is an important process in the process of automobile coating, which provides a complete primer coating for the whole vehicle to ensure that the salt spray resistance of the whole vehicle meets the requirements. However, various drawbacks in the process of electrophoresis of environmental protection electrophoretic paint seriously affect the corrosion resistance of the whole vehicle, so it is necessary to analyze and prevent the causes of various drawbacks. There are many kinds of defects of the electrophoretic paint film that may occur during the electrophoretic coating of automobiles, such as shrinkage, pinholes, roughness, particles, too thin film thickness, too thick film thickness, foreign matter attachment, etc. This paper mainly analyzes the causes of the defects of foreign matter attachment to the paint film.
1. Appearance of lump foreign body attachment
There are several cases of foreign matter attachment in the electrophoretic paint film, such as spot mark, yellow rust lump, etc. The causes are also many, such as poor degreasing of pretreatment, insufficient water washing, abnormal stoppage of pretreatment process, etc.
2. Characteristics of lump foreign body attachment
2.1 High hardness
This kind of foreign matter has high hardness, is not easy to damage and clean, and has strong adhesion with electrophoresis parts. It can be cleaned only by using scraper, pneumatic grinding wheel, etc.
2.2 The internal structure is honeycomb
Through the magnifying glass observation, the internal structure of the tumor is honeycomb-like, there are many bubble-like voids, the internal bubble distribution is uneven, and the bubble size is also inconsistent, the large diameter is about 6mm, and the small one is less than 1mm.
2.3 The position of occurrence is uncertain
The position of the tumor after electrophoresis is not constant. It may appear at any position on the top cover, door, door frame, bottom plate, etc., without obvious regularity. However, according to the position statistics, the probability of the occurrence of the door is slightly higher than that of other parts (see Figure 2). After the later analysis and verification, the main reason for the high probability of the occurrence of the tumor on the door is related to the tank liquid circulation state.
Automobile painting is a special process. There are many possibilities for the causes of the defects of the paint film of any car body painting. It needs to be considered and analyzed from the perspectives of human, machine, material, method and environment. If the problems are not frequent enough, it will easily lead to large hidden dangers and waste of tank fluid.
