Runoff occurs during the spraying of anti-corrosion coatings

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During the spraying of anti-corrosion coatings, sagging can sometimes occur, also known as dripping or flow-down. The coating thickens locally and forms droplets due to gravity, a phenomenon that occurs only when the sprayed surface is placed vertically or when spraying is carried out vertically. I. Improper use of diluents. It may be that a diluent with a slow drying speed was used, or an excessive amount of diluent was used. II. Improper use of the spray gun. For example, too low compressed air pressure, too short a distance between the spray gun and the surface to be sprayed, or too slow movement of the spray gun can all increase the likelihood of sagging. The beam shape and beam pressure should be adjusted appropriately to maintain a spraying distance of 20–25 cm, and the moving speed of the gun should be uniform. Determine the maximum spraying amount at which sagging occurs, and concentrate on spraying while observing the formation of the paint film. III. The temperature in the spraying workshop is too low, which makes it difficult for the anti-corrosion coating layer to dry; or the thickness of the coating applied in one go is too great, resulting in a slow drying rate of the anti-corrosion coating. IV. When applying subsequent coating layers, sufficient drying time should be allowed for the anti-corrosion coating layer applied in the previous step. Before placing the sprayed surface vertically, sufficient time should be allowed for the paint layer to settle and level out. When the sagging is mild, wait for the paint surface to dry, then gently sand the defective areas with fine sandpaper, and finally wax and polish them ； When sagging is severe, polish the defective areas and repaint them. In the event of sagging, the following repairs can be carried out: 1. If it occurs on a single-coat paint layer or varnish layer with a solid color, wait until the paint film has fully hardened, then sand it with P1200 or P1500 sandpaper. 2. If sagging occurs on the base paint layer, level out the sagging paint film and then spray paint again. 3. Countermeasures. (1) Choose high-quality paint materials and an appropriate amount of thinner. (2) The temperature and humidity of the construction environment are suitable. (3) The paint brushes selected should have elastic bristles that are thick at the base and thin at the tips, with thick hairs and even edges. The paint brush should be dipped in oil lightly but frequently. (4) During construction, the base layer should be made as smooth as possible, with any sharp edges removed. When brushing on the coating, apply it evenly with firm strokes; brush vertically first and then horizontally, avoiding random or messy application. (5) The appropriate thinner for the coating should be used. (6) Thoroughly clean the coated surface of debris such as dust, oil, water, and other impurities. (7) When the paint film has not fully dried and there is sagging of paint on one edge or side, an spatula can be used to remove the excess paint.