How to solve the defects of film surface shrinkage, shrinkage, depression and fish eye?

(1) phenomenon

Foreign matter (such as oil, water, silicone, etc.) existing on the surface of the object to be coated or mixed into the coating, the coating cannot be evenly attached, shrinkage occurs and the surface of the coating film is exposed, or the phenomenon of uneven injection of the coating film is called shrinkage cavity series. ills. Due to the great difference in the causes and phenomena, those with a large and irregular exposed area are called shrinkage cavities (commonly known as laughing, as shown in Figure 9_10); those that are round (mostly 0.1~2mm in diameter) are shrinkage cavities; Those with particles in the holes are called "fish limit".

Defects with a diameter of 0.5-3 mm are called depressions, depressions or pits, and pits on the surface of the coating film that do not expose the coated surface like a crater.

(2) Reason analysis

①The surface to be coated is polluted by water, light wax, polishing agent, dust, silicon inkstone, oil or lubricating oil. Contamination by residue from soaps, detergents or substrate finishes. This aspect is mainly after the body beauty, the cleaning procedure is not effective.

② Paint mixing equipment, Spray Guns and air pipes are not clean, so that harmful foreign matter is mixed into the paint.

③ After the surface preparation is completed, the surface to be sprayed or the wet paint film will be sprayed by the paint mist of different paints, especially the dry spray or paint mist, oil stains, polishing residues, etc. pollute.

④ The air in the painting environment is not clean, with dust, paint mist, silicon holes, sanding ash, wax mist ash, etc., or air pollution from neighboring factories. Prepared or wet painted surface.

⑤ Work clothes, gloves, etc. are not clean.

⑥The surface tension of the coating used is high, the leveling and air bubble release are poor, and the coating itself has poor shrinkage resistance or is mixed with foreign matter. (Related instrument: leveling meter)

(3) Preventive measures

① Before carrying out any work, it should be determined that the surface has been effectively cleaned.

② Any work involving silicone resin products should be carried out in a building separate from the painting workshop.

③Ensure that the compressed air is clean, oil-free and water-free. (Related instruments: Air Compressor)

④Ensure that the painting environment is clean, and there should be no dust, oil mist and paint mist floating in the air.

⑤ Equipment, tools, hoses and auxiliary materials for production in the painting workshop must not contain harmful substances that cause shrinkage cavities in the paint, especially organic silicon compounds.

⑥It is strictly forbidden to touch the painted surface with bare hands, dirty gloves and rags.

⑦ Choose paint with low sensitivity to shrinkage cavity. When spraying on the old paint layer, it should be fully sanded with sandpaper and wiped clean.

⑧In the case of slight shrinkage cavity, it can be improved by using multiple thin sprays.

⑨Choose an air hose suitable for painting. Contamination with organosilicon compounds may come from non-specially manufactured tubing. New paint or gas lines should be effectively cleaned before use.

(4) Remedy

Remove affected paint film and respray.