It mainly refers to the analysis and solution of defects caused by spraying iron red alkyd primer, iron red epoxy ester primer and iron red perchlorethylene primer.
1. Defects caused by iron red alkyd primer
There are mainly two defects: poor adhesion (instrument: adhesion Tester) and paint film peeling off. Poor adhesion is mostly caused by the oil stain on the surface of the base layer not being cleaned, and the water and oil powder in the compressed air used for spraying are filtered and mixed into the paint. The solution to avoid this phenomenon: First, effectively remove the oil on the surface of the metal substrate before painting; Second, the compressed air used for painting needs to be filtered through an oil-water separator to remove water and oil to ensure clean air.
The reason why the iron red alkyd primer peels off after the paint film is matched with the topcoat is mainly caused by unreasonable coating matching, such as spraying polyurethane topcoat on the surface of the iron red alkyd primer, because the alkyd primer The adhesion of the polyurethane topcoat is poor, and the adhesion of the polyurethane topcoat is strong. In the drying process of the polyurethane topcoat, it is easy to get the alcohol primer film, which will cause the primer to fall off or fall off in large pieces, seriously affecting the coating quality. The solution is to reasonably design the coating matching, such as polyurethane topcoat, should use iron red epoxy ester primer or iron red acrylic primer with strong adhesion instead of iron red alkyd primer with poor adhesion Or iron red vinyl chloride primer as a primer to prevent the paint film from falling off.
2. Defects caused by iron red epoxy ester primer
The main defects of this kind of primer in the spraying process are exposed bottom, flowing and sagging. The reasons for the exposed bottom: First, the viscosity of the paint (instrument: Viscosity Cup) is adjusted too thin, so that the paint film after spraying is too thin and the coverage is poor, resulting in exposed bottom; Second, the moving speed of the Spray Gun is too fast during spraying. The thickness of the paint film ( Instrument: paint Film Thickness Gauge) is not uniform, and the bottom is exposed at the thin part. Therefore, when thinning, strictly control the spraying viscosity to not be less than 18 seconds, and use longitudinal overlapping method or horizontal and vertical alternating method when spraying. The bottom can be prevented.
The reasons for the flow and sagging of spraying: one is that the distance between the Spray Gun and the surface to be sprayed is too close during spraying; the other is that the air pressure is too high and the moving speed of the Spray Gun is too slow during spraying. Therefore, when spraying the iron red epoxy ester primer, in order to prevent the paint film from flowing and hanging, the air pressure should be controlled within the range of 0.025~0.35MPA (2.35~3.5kg/c㎡!), and the spraying interval should be 20~30 Within centimeters; the moving speed of the Spray Gun should be uniform, not too fast or too slow.
3. Defects caused by iron red perchlorethylene primer
The defect caused by spraying iron red perchlorethylene primer is mainly poor adhesion, which belongs to the problem of the paint itself. Therefore, when matching, it cannot be matched with polyurethane and other strong adhesion topcoats to prevent peeling of the primer.
