Causes of metallic paint scars and their prevention methods
- 2019-06-13-

Affected by the "flop" effect (different brightness and color as the investigation angle changes), whether it is water-based metal paint or solvent-based metal paint, it is particularly prone to occur during the spraying process, which is easy to occur during spraying. The condition is the "spot" of the paint film.
"Scar" is a kind of paint film damage caused by uneven metal light and different color shades caused by various reasons in the process of coating. Metal paint marks are generally divided into spray marks, pollution marks, and back spots. The characteristics of spray marks are that after the metal paint is sprayed, the surface of the film shows uneven block marks; the stain marks are the substrate after the metal paint is evenly sprayed. The effect of the pollutants is plaque in the unfixed part; the back stain is the phenomenon that the metal aluminum powder in the metal paint is free when the varnish is applied after the metal paint is applied, and enters the varnish film layer to form a color unevenness.
Causes of spray marks: The spray gun is not evenly sprayed when spraying metal paint: 1. The paint after the metal paint is sprayed is not enough; 2. The medium coating is not well polished, not finely lubricated, and the appearance quality is poor. , and the color of the metal base paint is not matched; 3. The metal paint uses a thinner that evaporates very slowly, or the amount of thinner is too much.
Causes of contamination marks: residual water marks, perspiration or post-touch pollution after polishing, these residual pollution can not be seen visually, the subsequent viscosity is not scrubbed, and the effect pigments are disordered at the contaminated part after spraying the metal paint. Placed.
The reason for the back spots is that after the metallic paint is applied, the metal particles and the pigment particles are placed in an orderly manner in the coating film. After the varnish layer is applied, the solvent in the varnish dissolves the metallic paint layer, and the metal particles and the pigment particles are released according to the turbulent flow phenomenon, and enter the varnish coating film.
Prevention of scars 1) Prevention of spray marks In the construction of metal varnish, the parallel orientation of the aluminum powder on the substrate is affected by the solvent movement in the paint film. At the site application viscosity, approximately 85% of the solvent overflowed during the monotonic process of the color primer. The solvent evaporates on the exterior of the paint film to cause changes in the external tension. At the same time, when the primer is monotonous, the solvent in the paint film continuously moves from the bottom to the outside to form a turbulent or turbulent flow. In the paint film, the pin powder is affected by the turbulence, and is no longer placed in parallel. After all, the "frozen" is in a skewed orientation. It is assumed that during the construction of the metallic varnish, there is a lot of solvent when the primer is touched with the substrate, and this movement is intense in the monotonous process of the primer film. On the contrary, if there is less solvent in the construction process, the orientation process of the aluminum powder sheets placed in parallel will not be greatly affected. Therefore, the color primer is selected to be "dry spray" to reduce turbulence in the film formation process, thereby achieving a large metallic light effect. It is preferred to summarize the above-mentioned various elements, and to apply a dry spray coating and a matting varnish wet spray. In addition, in the detailed construction method, it is required to be several times, each layer is thin, and multiple times of spraying, instead of a thick film construction method, the flashing time is sufficient, so that the solvent is fully evaporated, so that the solvent is as much as possible before the varnish is applied. Evaporate out.
2) Contamination marks The pollution before the color paint is mainly caused by polishing ash, touch, water stains, sand marks and putty. Scrubbing after scrubbing and viscous cloth scrubbing before use can be useful to remove the ash. Touching the sweat that has occurred, the skin-modified cosmetics, and the residual water stains are difficult to erase. You can use anhydrous alcohol and isopropyl alcohol to scrub. The proper application of fine sandpaper in the middle coating can improve the sanding marks, and spray a layer of quick-drying primer in the direction of the sanding marks and the putty to fill and cover.
3) Control of back stains Select the appropriate thinner according to conditions such as temperature. The monotonic speed of the thinner selected for the metallic paint is relatively faster, and the monotonic speed of the thinner used in the varnish should be suitably slower. The metal base paint adopts a low boiling point solvent (mainly toluene, adding a small amount of ethyl acetate, etc.), so that the base paint film adheres to fast drying. Most varnishes use non-polar solvents (mainly aromatic solvents).
The solvent in the metallic paint coating is evaporated and the varnish is applied afterwards. In general, when the solvent evaporation amount of the solvent-based metal base paint film is more than 95%, the dehydration rate of the water-based paint reaches 85%, and the varnish is sprayed.
Due to its sheet-like structure, silver powder has a problem in the guessing. The silver powder is assumed to have poor control, the color is not up to the requirement, and it is not easy to construct, and it is easy to cause stains and affect the decorative effect.