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（1） The top coat foams after baking

 

Scrape off the bubbles after the top coat bubbles, and see which layer the bubbles are on. If the bubbles appear in the primer layer, the putty and the primer are well combined, and the substrate treatment may not be in place; after scraping the bubbles, it is found that there is a layer of primer on both the putty and the substrate, so it may be that the primer is too thick or the primer is not completely dry.

 

（2） Pinholes and pits appear after baking

 

First of all, whether the quality problem of atomic ash itself caused pinholes was considered. Secondly, if the quality of the putty is qualified, the pinholes are generally due to the poor scraping and grinding technology of the putty, and the sand holes are not handled properly. In addition, in the process of coating and scraping, if the coating tool is not selected properly, pinholes will also be caused.

 

（3） "Prickly heat" after baking the top coat

 

First, the climate is too humid, and the water absorption rate of atomic ash is too large. The polished atomic ash absorbs a considerable amount of water. Before the water volatilizes, the top coat is sprayed. A small amount of water is sealed under the paint film. Once heated, the water volume expands rapidly, breaking through the paint film to form "prickly heat".

 

Second, the water absorption of atomic ash is qualified. After hot air drying, the top coat is sprayed, and "prickly heat" appears after baking. Then, it is possible that after spraying the top coat, the solvent will enter the drying room before the solvent is fully volatilized. In this way, as the surface of the topcoat is closed quickly, the residual solvent has to break through the paint film to form "prickly heat". Of course, it may be the quality of the topcoat, or the polarity of the solvent does not match the topcoat, resulting in "prickly heat".

 

（4） Cracking of putty or primer

 

In the paint repair area, the putty filled area or primer layer cracks, resulting in the cracking of the top coat.

 

reason:

 

① The thickness of the putty layer or intermediate primer layer is too thick, and the drying time between each layer is not sufficient, which makes the surface of the putty layer or intermediate coat primer layer dry and the bottom layer soft, resulting in the cracking of the putty layer or intermediate primer layer. Therefore, in the process of putty scraping or primer spraying, thin layer and multiple construction should be adopted, and enough drying time should be reserved according to the climatic conditions.

 

② The transition zone between the primer coat of putty or intermediate coat and the old paint layer, i.e. the periphery of feather edge, is not fully treated, which leads to the incomplete bonding and cracking of the putty coating. 600 sandpaper should be used to avoid the solvent being brought into the deep scraping layer of the lower layer.

 

③ The thinner used in the primer does not meet the requirements, resulting in the primer layer is not easy to dry or excessive shrinkage and cracking.

 

Correction method:

 

Grind the cracked area thoroughly, scrape AFR and spray primer and topcoat, and pay attention to leave enough drying time between coatings.