Common paint film defects and solutions of container coatings

集装箱生产过程中常见的漆膜弊病和解决措施见表。

漆膜弊病	产生原因	解决措施
流挂	涂膜厚度过厚: 控制不当造成涂膜厚度过厚；喷涂枪嘴型号不合理，扇幅宽度过窄或出漆量过大；车速过慢；枪口距被涂物距离过近；喷涂压力过高	控制涂膜厚度在合理范围内；选择合适的枪嘴；提高车速在合理的范围内；增加枪口距被涂物距离；降低喷涂压力
	施工黏度过低(兑稀率过高)	提高施工黏度(减小兑稀率)
	钢板打砂密度及粗糙度过低	提高钢板打砂密度，打砂粗糙度控制在合理范围内
	溶剂挥发速率过慢；溶剂本身挥发速率过慢；环境温度低造成溶剂挥发过慢	使用快干稀释剂，提高溶剂挥发速率
	涂料本身杭流挂性过差	提高涂料抗流挂性，如加入防流挂助剂等
针孔	搅拌或喷涂产生的气泡喷涂至钢板表面，气泡破裂后涂膜不能及时流平	在涂料混合搅拌后，静置一段时间至容器内气泡完全消失，或在涂料中加入消泡助剂减少气泡的产生
	涂膜表干过快，底层溶剂挥发不畅；溶剂挥发过快，造成表干过快；底漆或中间漆溶剂挥发过慢，面漆表干后，下层涂料溶剂仍未挥发完全；涂膜厚度过厚，表层涂料已经表干，下层涂料溶剂仍未挥发完全；通风过度造成涂膜表干过快；流平工位过少，造成流平时间不足，进人烘房后涂膜表干，但下层溶剂仍未挥发完全；初期烘烤温度过高	Select a solvent with an appropriate volatilization rate so that the upper coating solvent does not volatilize too quickly, while the lower coating solvent does not volatilize too slowly; control the thickness of the coating film within a reasonable range; reduce the air surface velocity after construction, such as reducing the fan power, etc. , increase the leveling time; reduce the initial baking temperature, such as setting a low-temperature drying room to ensure that the solvent evaporates, and then enter a high-temperature drying room to ensure that the coating film is dry
	The paint cannot completely cover the base material or the lower layer of the coating film, forming pinholes at the bottom; the construction viscosity is too high (the dilution rate is too low); the spraying pressure is too low; the vehicle speed is too fast; the nozzle model is not properly selected, resulting in poor atomization ; The distance between the gun nozzle and the object to be coated is too far; the airless sprayer compressor pump filter is blocked, resulting in insufficient paint output; the coating itself has poor wettability to the substrate or the underlying coating film	Adjust the construction viscosity, spraying pressure, vehicle speed and the distance between the nozzle and the object to be coated to a reasonable range; select the appropriate nozzle model; clean or replace the filter of the compressor pump of the airless sprayer; increase the wetting of the paint to the substrate or the underlying paint Capability, such as adding wetting and dispersing agent, etc.
Shrinkage cavity	Shrinkage caused by pollution; contamination of the base material or the lower layer of the coating film causes excessive surface tension, resulting in shrinkage cavities after the upper layer of coating is applied; the mixing of impurities, such as oil or water, causes excessive local surface tension after the coating is applied. large, resulting in shrinkage	Pay attention to the cleanliness of the substrate and strictly prevent impurities from contaminating the substrate, underlying coating film or paint
	Excessive drying of the underlying paint, resulting in excessive surface tension of the underlying paint	Reduce the baking temperature or baking time of the lower coating, so that the "mutual dissolution" phenomenon occurs between the upper and lower coatings, so as to avoid the occurrence of shrinkage cavity
	In the process of manufacturing coatings, low surface tension additives, such as silicone-based defoamers or leveling agents, are added in too large amounts, resulting in shrinkage cavities from the surface	Add appropriate leveling aids to reduce the surface energy of the coating, thereby reducing the occurrence of shrinkage. However, if the shrinkage is caused by adding low surface tension defoamers or leveling agents, the use of such aids should be reduced or avoided. agent
	Poor miscibility between solvent and paint	Increase the solubility of solvents
orange peel	Construction viscosity is too high (too low dilution ratio)	Reduce the construction viscosity and increase the dilution rate
	Spray pressure too low	Increase spray pressure
	too fast	reduce speed
	Improper choice of nozzle model, resulting in insufficient atomization	Choose the right nozzle model
	The Spray Gun is too far away from the object to be coated	Reduce the distance between the Spray Gun and the paint
	Solvent evaporates too fast	Reduce solvent evaporation rate, use slow drying thinner
	hyperventilation	Reduce air surface velocity after construction and reduce fan power
	Too few leveling stations, resulting in insufficient leveling time, enter the drying room	Increase leveling time or decrease initial bake temperature
	Substrate or underlying paint temperature too high	Increase the cooling time after the substrate or the underlying coating film is baked
	Poor leveling of the paint itself	Adding leveling aids to coatings
whitening	Solvent evaporates too fast	Reduce the evaporation rate of solvents, use high boiling point solvents or slow drying thinners
	Excessive relative humidity, such as rain	When the relative humidity is high, try to avoid direct exposure of the incompletely dried coating film to the air. In rainy weather, the completely dried coating film should also be covered
	The paint itself has poor water resistance	Adding surface additives to the paint to increase the water resistance of the surface
to crack	Cracking caused by too large difference in shrinkage rate or too large difference in softness and hardness between the primer and the top coat during the film forming process, such as spraying the top coat (especially the two-component polyurethane surface) before the primer is dry paint), that is, "wet-on-wet" construction, because the shrinkage of the topcoat is greater than that of the primer during the drying process, resulting in cracking	Increase the baking time and baking temperature of the intermediate paint, or increase the leveling time of the intermediate paint, or add a quick-drying thinner to the intermediate paint. When spraying the top coat, use the intermediate paint to reach or exceed the surface dryness to prevent cracking increase the sanding roughness of the steel plate, increase the adhesion of the substrate to the coating film, and prevent cracking
	The ambient temperature is too low. When the container is on the production line, the coating film is at a relatively high temperature, and it is suddenly placed outdoors where the temperature is too low. The coating film cracks due to "thermal expansion and contraction"	Increase the storage time of the container at the exit to prevent sudden cooling
	The surface coating is too brittle, and the coating film cracks due to bumps during container handling	Add toughening additives to the surface coating to prevent the coating film from being too brittle
poor adhesion	The adhesion of the coating film to the substrate is poor; the steel plate is polluted in a large area, such as oil stains, etc.; the roughness of the steel plate is poor or the sanding density is too low; the steel plate after sanding is not sprayed with zinc-rich primer or zinc-rich paint spray film in time Insufficient thickness, resulting in corrosion of the steel plate	Strictly prevent the pollution of the steel plate, if necessary, clean the steel plate or burn it to remove oil; increase the sanding density and roughness of the steel plate; spray the zinc-rich paint in time after the steel plate is sanded, and control the thickness of the zinc-rich paint film to prevent it Low, for the steel plate that has been corroded, it should be re-sanded and sprayed with zinc-rich paint
poor adhesion	Poor interlayer adhesion of the coating film; over-drying of the primer; when refinishing after the topcoat is completely dry, the underlying coating is not re-sanded; the underlying coating contains too much low surface tension additive	Shorten the construction interval between the surface coating and the primer coating, and use the "wet-on-wet" construction process if necessary; when repairing the completely dried coating film, it should be re-polished; reduce the amount of low surface tension used in the coating

Products required

WAPT-II aluminum foil pinholing degree Tester
$ 534.00

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