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4 Higher requirements for the cleanliness of the painted surface
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For these defects, corresponding solutions have been specially researched and formulated.
3.
1 Sagging (Figure 2)
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Solution: Lower the ambient temperature or dilute the paint.
Cause 2: The relative humidity of the spraying environment is too low (<40%).
Solution: increase the environmental humidity or dilute the paint.
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4 Spots (Figure 5)
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It can be seen from Figure 1 that an environment with a temperature of 15 to 35 ℃ and a relative humidity of 45% to 70% is most suitable for the construction of water-based coatings.
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4 Higher requirements for the cleanliness of the painted surface
In the following cases, water-based paint spraying needs to increase vehicle preheating, hot air supply, paint preheating and other treatment processes.
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3 Coating film defects and treatment methods
According to the research and spraying experience of water-based coatings, the following defects are common in water-based coatings.
For these defects, corresponding solutions have been specially researched and formulated.
3.
1 Sagging (Figure 2)
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Cause 1: The temperature of the spraying environment is too low.
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Solution: preheat the surface of the substrate before spraying, heat the spray booth with hot air (above 12 ℃), and preheat the coating material.
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Reasons for formation: the combined factors of too thick one-time spraying, too high drying temperature and too short flash time.
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Cause 1: The temperature of the spraying environment is too high (>40 ℃).
Solution: Lower the ambient temperature or dilute the paint.
Cause 2: The relative humidity of the spraying environment is too low (<40%).
Solution: increase the environmental humidity or dilute the paint.
3.
4 Spots (Figure 5)
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Cause 1: Contaminants exist on the surface of the substrate.
Solution: Strengthen the cleaning of the surface of the substrate to ensure that the oil, flaw detection fluid and other contaminants are cleaned up.
Cause 2: Grease is mixed in the spray material.
Solution: Before switching to water-based paint, the paint mixing tank, spraying equipment and piping system that use solvent-based paint should be thoroughly cleaned.
It is recommended to soak it with epoxy paint thinner or polyurethane paint thinner with strong solubility for more than 1 h, then clean the paint sprayer and piping system, and finally rinse with clean tap water until the washing water is colorless and no obvious oily stains.
3.
5
Reasons for paint peeling 1: The oil and other impurities on the surface of the substrate have not been cleaned up.
Solution: Strengthen the cleaning of the surface of the substrate to ensure that the oil, flaw detection fluid and other contaminants are cleaned up.
Cause 2: The temperature is too low or the relative humidity is too high during spraying.
Solution: According to the environmental temperature and humidity, increase the surface preheating, spraying room to send hot air (above 12 ℃), drying and other operations.
Conclusion
Through the research on the performance characteristics and construction technology of water-based coatings, a method to deal with coating film defects is proposed.
By formulating process specifications suitable for the construction of water-based coatings for railway freight cars, the problem that the construction technology of water-based paints for railway freight cars is not yet mature has been effectively solved.
Lays a technical and theoretical foundation for the comprehensive promotion and application of water-based coatings on railway freight cars and the realization of green manufacturing.
