In order to obtain a good and stable intermediate coating, the following points should be paid attention to.
(1) The selected intermediate coating should have good compatibility with the primer and top coat, and there should also be good bonding between the unpolished intermediate coating film and the top paint film . The strength of the intermediate coating film should be similar to that of the topcoat, and the drying temperature should be the same as or slightly higher than that of the topcoat.
(2) The quality and cleanliness of the surface of the primer should be checked before the intermediate coating, and all should meet the process requirements. When there is no pre-drying process on the PVC line, the ostrich hair automatic cleaning machine cannot be used, but manual cleaning. Defects (such as particles, splashes of PVC paint, etc.) on the body surface entering the intermediate coating line should be eliminated.
(3) The operating requirements and technical specifications of the selected coating method (such as manual air spraying method, manual electrostatic spraying method and high-speed cup automatic electrostatic coating method, etc.) should be strictly followed . (4) The painting environment should be the same as that of the topcoat, to be clean and dust-free (both are discharged under the clean air-conditioning wind, the lighting above 800lx, and the vertical wind speed is 0.45~0.5m/s in a large spray booth for spraying ), which can reduce or eliminate the disadvantages of the intermediate coating, so as to reduce the grinding workload of the intermediate coating or realize the non-grinding of the intermediate coating.
(5) The grinding of the intermediate coating should be regular, and the grinding direction should be consistent, and should not be ground randomly. Use 400 # ~ 800 # water sandpaper for wet grinding. Do not grind the coating through to expose the bottom metal surface. Primer should be reapplied after painting the topcoat to enhance the rust resistance of this part and the adhesion of the topcoat.
