filmWithLacquer liquiddownflowThe phenomenon of traces is called sagging.More often inVertical planeorAngularityAt.Generally appearing in the vertical plane isVertical curtain hanging, those appearing at corners areTear like sagging。BrushedfilmIf the paint is too thick or too thin, sagging will occur.
1. Improper construction, the spray gun is too close to the coated surface.
2. The gun moving speed is too slow, and the one-time spraying is too thick.
3. The viscosity of paint construction is low.
4. The construction environment temperature is low and the paint drying time is slow.
5. AdoptionWet to wet processWhen spraying, the interval time is too short.
6. The spraying pressure is lower than the process range, and the diameter of the spray gun is too large.
(1) Excess diluent makes the viscosity lower than the normal construction requirements, and the paint cannot be attached to the surface of the object and flow down.
(2) The temperature of the construction site is too low, the drying speed of the paint is too slow, and the fluidity in film formation is large.
(3) The selected paint brush is too large, too long, too soft, or too much oil is dipped and too much paint is brushed, so that the thickness of the paint varies, and the thicker part will flow
(4) The unevenness of the painted surface or the grooves of the edges, corners, and line corners of the objects are easy to cause uneven brushing and uneven thickness.[1]
preventive measure
Announce
edit
1. Use the correct spraying method and adjust the spray gun properly.
2. Dilute the paint according to the mixing ratio as far as possible to keep the construction viscosity within the process range.
3. During construction in winter when the temperature is low, try to increase the temperature of the spray booth to ensure that it is above 10 ℃ to room temperature.
fourWet to wet processSufficient interval shall be ensured during construction.
5. The pressure and caliber of the spray gun shall meet the process requirements.[1]
Repair method
Announce
edit
1. When it occurs in the finish coat or varnish coat of the solid color single process, after the paint film has completely hardened, it shall be polished with P1200 or P1500 sandpaper,
2. When the base color paint layer is sagging, it shall be re sprayed after polishing the sagging paint film.
3. Countermeasures.
(1) Select excellent paint materials and appropriate diluent.
(2) The construction environment temperature and humidity are appropriate.
(3) The selected paintbrush and brush hair should be elastic, with thick root and thin tip, thick mane and even mouth.The oil brush shall be dipped lightly and frequently.
(4) During construction, the base course shall be as flat as possible and the edges and corners shall be removed.When brushing, brush evenly with force, first vertically, then horizontally, and do not smear horizontally
(5) The matching thinner of the paint shall be selected.
(6) Thoroughly clean the debris, oil, water and other sundries on the coated surface.
(7) When the paint film is not completely dry and the paint falls on one edge or one surface, the excessive paint can be removed with a blade[1]
Automobile coating sagging
Announce
edit
Sagging is a paint film quality problem often encountered in the process of automobile coating production. There are many factors causing sagging: paint characteristics, construction environment, personnel skills, spraying equipment and process parameters are closely related.
resolvent
1. Select the solvent correctly, reduce the content of slow solvent, pay attention to the solubility and volatilization speed of solvent, and remedy sagging defects by mixing with new paint containing less slow solvent.
2. The proficiency of spraying operation shall be improved, and the spraying shall be even. It is not suitable to spray too thick at one time.During spraying, the construction parameters can be controlled by increasing the air pressure, increasing the distance between the spray gun and the workpiece, increasing the flash time between the two layers of coating, reducing the paint flow speed, using smaller nozzles, increasing the rotating cup speed, improving the degree of paint atomization, reducing the size of paint mist droplets, etc.
3. Strictly control the application viscosity of paint;Strengthen air exchange, keep the ambient temperature at the construction site above 15 ℃, and strictly control the ambient temperature for coating construction and paint mixing.
4. Adjust the formula, use additives correctly, and increase the amount of anti sagging agent.
Leveling property, surface tension, volatilization rate of residual solvent and solubility of residual solvent are all coating properties determined by formula.However, the proportion of residual solvent is only affected by the formula to a certain extent, which largely depends on the atomization process.[1]
Inspection regulations
Announce
edit
The national standard GB/T9264-88 "Determination of sagging of paints" test method uses a sagging tester to measure the sagging of paints. The film thickness of a strip film placed vertically and not flowing to the next thickness is the value of no sagging. The greater the thickness value, the less likely sagging will occur.[1]
Avoidance measures
Announce
edit
Superfine barium sulfateThe amount of base material required is low, which can be used as a rheology control agent to increase the solid content of the coating, reduce VOC and prevent the sagging of the coating to a certain extent.This superfine barium sulfate has been usedWood Coatings andAutomotive CoatingsMedium.
