The poor hiding power of the coating film includes not only the powder coating itself, but also the improper control of the powder spraying process. If the covering power of the coating film is poor, there will be poor bottom covering or exposed bottom that cannot completely cover the color of the bottom surface.
1. The reason of powder coating itself
If the amount of pigment with hiding power is not enough when designing the powder coating formulation, the formed coating film will have no covering power.
2 Reasons for the coating process
The thickness of the coating film has a direct impact on the hiding power. If the coating film is too thin (below 40-50µm), the problem of poor hiding power will easily occur. Therefore, it is necessary to increase the covering power by improving the spraying process and increasing the thickness of the coating film. Moreover, the coating film with a certain thickness has good leveling property, is not prone to problems such as particles (particles), and has good physical and mechanical properties of the coating film. However, the coating film should not be too thick. Too thick coating film will increase the amount of coating and the cost of coating.
In the electrostatic powder coating process, the methods of controlling the thickness of the coating film are:
① Select the appropriate number and arrangement of Spray Guns in the spray booth;
② Adjust the powder output and air pressure of the Spray Gun;
③ Adjust the running speed of the conveyor chain;
④ Correctly arrange the hanging method of the object to be coated. Among them, the powder output of the Spray Gun and the degree of atomization are important factors, so a powder supply device with high powder supply accuracy should be selected. When spraying coatings with complex shapes, it is difficult to be sprayed in order to prevent the recessed parts from being affected by Faraday shielding. A special corona Spray Gun with electrodes inside should be used or a tribostatic powder Spray Gun should be used.
