The first is that the prepainted galvanized steel coil does not reach the expected gloss;
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The second is that the surface of the prepainted galvanized steel coil has different shades of color;
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The third is that after a period of time, the coating surface of the prepainted galvanized steel coil has a decrease in gloss or inverted light phenomenon;
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The fourth is that the color of the prepainted galvanized steel coil after curing is darker than expected.
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Problems with the coating formula of the prepainted galvanized steel coil. There are too many pigments, fillers and solvents in the paint, and the fineness is not enough or there is dust;
The surface of the prepainted galvanized steel coil substrate is rough or has oil, moisture, wax and other substances, and the coating is not completely cured;
The paint is not stirred sufficiently before being put on the machine, and the solids of the paint sink to the bottom of the barrel, resulting in less pigment in the barrel during construction;
Excessive diluent is added to the paint, diluting the effect of the glossy paint;
The surface coating of the prepainted galvanized steel coil is too thin, and the roller coating room temperature is too high or too low during construction;
The temperature of the curing furnace is set too high, the hot air circulation in the furnace is insufficient, and the coating is over-baked, causing the color to age and the gloss to decrease.
In order to avoid poor gloss of prepainted galvanized steel coil, we at Li Cheung Steel will do the following checks before production:
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Check whether the fineness of the paint on the machine meets the process requirements.
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The paint should be fully stirred and filtered before being put on the machine, and the thinner should not be added too much.
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Control the humidity of the roller coating room to prevent moisture from mixing into the coating,At the same time, the temperature of each section of the curing furnace should be set reasonably to avoid being too high or too low.
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Check whether the thinner matches the paint to ensure the wet film thickness of the topcoat, which should not be too thin.
