Technical data
Table 4-1. Spray Coating Troubles, Possible Causes, and Remedies - Continued
Trouble Possible Causes Preventive Measures Or Remedies
Paint Leaks from
Spray Gun (Fig-
ure 4-12)
1. Fluid needle packing nut too tight. 1. Loosen nut, lubricate packing.
2. Packing for fluid needle dry. 2. Lubricate this part daily.
3. Foreign particle blocks fluid tip. 3. Remove tip and clean.
4. Damaged fluid tip or needle. 4. Replace both tip and needle.
Gun Sputters Con-
stantly (Figure
4-13)
1. Fluid nozzle not tightened to the spray gun. 1. Tighten securely, using a good gasket.
2. Leaking connection of fluid tube or needle
packing (suction cup).
2. Tighten connections; lubricate packing.
3. Fluid pipe not tightened to the pressure
tank lid.
3. Tighten. Check for defective threads.
Orange Peel (Fig-
ure 4-14)
1. Coating material not thinned out suffi-
ciently.
1. Add the correct amount of solvent by
measure or viscosity test.
2. Coating material too cold. 2. Heat material to get flow-out.
3. Insufficient air pressure. 3. Increase air pressure or reduce fluid pres-
sure.
4. Using wrong air cap or fluid nozzle. 4. Select correct air cap and nozzle for the
material and feed.
5. Gun stroked too far from the surface. 5. Stroke the gun 6 to 10 inches for HVLP
gun from surface.
6. Overspray striking a previously sprayed
surface.
6. Spray detail parts first. End with a wet
coat.
Sandpaper Finish
(Figure 4-15)
1. Unsatisfactory wash primer or primer. 1. Laboratory analysis to verify acceptability
of the material; check wash primer and
primer application procedures.
2. Excessive dirt contamination from painting
area.
2. Provide cleaner painting areas.
3. Insufficient scuff-sanding of primer. 3. Scuff-sand primer using No. 320 and No.
400 wet or dry sandpaper.
4. Improperly cleaned paint lines. 4. Flush paint lines frequently with solvent.
5. Dried overspray, gun too far from surface. 5. Sand the complete finish until smooth to
the fingertips. Stroke gun 6 to 10 inches
for HVLP gun from the surface.
Wrinkling (Figure
4-16)
Caused by applying too thick a coating,
this prevents uniform drying of the coat
and thus results in formation of ridges
and furrows.
Material should be applied in thin uniform
coats. If a thick coating is necessary, it
should be applied by spraying several
thin coats until the desired thickness is
obtained. Allow each coat to set before
applying the next.
TO 1-1-8
Change 2 4-15