1. Color difference
(1) phenomenon
The hue, lightness, and chroma of the newly painted paint film are different from the standard color plate, or are different from the original paint color during repair painting, which makes the difference between the repaired area and the original car paint film prominent, resulting in "body paint layer patch” perspective. This coating defect is common in repair coating, as shown in Figure 9_l6.
(2) Reason analysis
① The reason for the color difference on the new car painting line is the color difference between batches of paint. (Related instrument: Colorimeter)
②The finished gun is not cleaned when the color is changed.
③ Improper drying and leveling specifications cause over-drying.
④ In the case of repair coating, the color adjustment accuracy is not enough.
⑤ When the topcoat is partially repaired, the technique may be improperly mastered, resulting in spot marks.
⑥The coating is also prone to chromatic aberration due to color bleeding, floating color, sinking color and other reasons.
Second, the metal flash color is uneven
(1) phenomenon
When spraying metallic flash color finish paint, due to poor dispersion of aluminum powder, uneven distribution, and uneven orientation, the phenomenon of uneven coating surface is called uneven metallic flash color.
(2) Reason analysis
① Improper coating formula (such as low aluminum powder content, high density of solvent, low relative molecular weight of resin, slow finger-touch drying of resin, etc.).
② Improper choice of spraying viscosity (too low or too high).
③The coating is too thick or the coating film is uneven, the atomization is poor, and the spraying operation is not skilled. (Related Instruments: Thickness Gauge)
④ When the "wet-on-wet" process is used for the base color and the varnish, the drying time in the middle is too short.
⑤The ambient temperature is low
(3) Preventive measures
① Improve the paint formula and use the solvent specified by the paint factory.
②Choose the appropriate spraying viscosity (can be obtained through experiments).
③ To improve the proficiency of spraying operation, use special spraying tools (Spray Gun with agitator).
④Choose the "wet to wet" process when it is suitable for drying or increase the process of blowing hot air at 60~80°C. (Related instrument: drying time Tester)
⑤ Adjust the ambient temperature during spraying to an appropriate range.
(4) Remedy
Same as 13, l4 coating defects.
