Pinhole delamination occurs on the surface as a needle punches through a small hole. From the theoretical analysis, there are three reasons for the formation of pinholes:
① There is moisture and oil on the surface of the box when painting;
②The surface temperature of the box is too high, causing the surface of the coating to dry too quickly, and the solvent and sea thinner inside the coating cannot be released in time (relevant equipment: drying time Tester)
③The paint film is too thick in one call (relevant instrument: Thickness Gauge ) , or the pressure of the test is not enough when the high-pressure airless paint is used, resulting in poor paint curing state.
In container coating, it is mainly the second reason that pinholes are formed in the coating. According to the author's practice, it is found that there are two kinds of "pinholes" on the coating film of the container. One is that the "pinholes" directly reach the steel substrate. When a "pinhole" scanner is used to detect, an alarm will sound. It is also more difficult to coat the “holes” because not only the area is large, but also a layer of container paint is applied again, and the “pinholes” cannot be stopped quickly, and the pinholes become bigger and bigger. In this case, when using one-component vinyl It often happens that the bottom surface of a container is made of aerated rubber for deep matching, and the anti-rust performance of the coating film will be seriously affected. Another kind of "hole counting" is simply caused by the disadvantages of coating on the outside rattan, and the base point of "pinhole" is Not on the steel plate, but on the epoxy intermediate paint. Especially in midsummer, the temperature of the box is high (related instruments: temperature measuring paper/temperature sensing sheet), and if the chlorinated rubber topcoat is too thick once sprayed, it will be damaged inside the coating. The organic solvent gas is too late to volatilize to form "pinholes". For this kind of pinholes, the treatment is relatively simple. The surface of the coating is polished with fine sandpaper, and then a thin layer of chlorinated gum (or propane acid) is sprayed on the outside. paint it,
