In the process of vacuum coating process, UV topcoat is an indispensable link. The main function and function of UV topcoat is to protect the electroplating layer and prevent the metal film layer from being oxidized and blackened after contacting with air; increasing the hardness of the product surface, To ensure that the electroplating products can meet the weather resistance function under various conditions; in addition, different proportions of color essence, color paste or matte oil can be added to the topcoat to achieve the purpose of controlling the appearance color and gloss of the vacuum electroplating finished product.

Analysis and countermeasures of problems that are easy to appear in the process of topcoat spraying:

1. Topcoat peeling off:

Analysis of the reasons: incomplete evaporation of the solvent in the topcoat, contamination of the coating layer, incomplete curing of the topcoat, incompatibility between the topcoat and the primer;

Improvement measures: reduce the line speed, increase the leveling temperature and leveling time of the topcoat, and reduce the coating thickness of the UV topcoat;

The product should not be placed for too long after coating, and the surface of the semi-finished product that has not been painted after coating should be kept clean;

Measure whether the energy of the UV lamp meets the requirements and whether it is working normally;

Replace with a topcoat that is compatible with the vacuum plating primer.

2. Surface particles of topcoat:

Analysis of the reasons: the air or paint is polluted, and impurities are mixed; the time after vacuum coating is too long, the metal coating layer is polluted and acidified;

Improvement measures: improve the dust-free level of the environment, replace the filters at all levels in the air supply equipment, improve the cleanliness of the compressed air, recognize the positive and negative pressures of the spray booth and the curing section, and ensure that the wind pressure of the clean air is greater than that of the normal air. Pressure; increase the number of filtration times and the number of meshes of the filter screen before the coating is used to ensure the cleanliness of the coating; after coating, spray the topcoat as soon as possible to prevent the coating layer from being polluted and acidified.

3. Shrinkage phenomenon, the surface of the topcoat shows a "crater" phenomenon:

Analysis of the reasons: The coating layer is polluted or oxidized after electroplating, the compressed air is polluted, the paint is polluted, the vacuum coating chamber is polluted, and the coating layer is polluted, and the spray gun or the compressed air pipeline is polluted;

Improvement measures: organize and maintain the coating room of the vacuum electroplating machine, check the pollution source of the coating layer, and spray the topcoat immediately after the vacuum coating; check and ensure that the oil-water separator of the air compressor is working properly; appropriately participate in the anti-shrinkage help in the topcoat coating. agent; clean the paint spray gun and compressed air lines.

4. Color spots, color circles, accumulated color, uneven color of finish:

Analysis of the reasons: the compatibility of dyes such as color concentrate and color paste is not good; the diluent component in the topcoat is too much; the compressed air pressure is too low or too high; the amount of fuel injection is too large and the spray is too thick;

Improvement measures: replace the type and brand of dyes such as color concentrate or color paste; reduce the proportion of thinner and increase the solid content of the paint; adjust the air pressure of the spray gun and the distance between the spray gun and the product to ensure a good atomization effect; The topcoat should be sprayed as thin as possible under the condition of being flat and satisfying the reliability requirements of vacuum coating.