1. The equipment used should be suitable for the intended purpose, capable of properly
atomizing the paint to be applied, and outfitted with the required pressure regulators
and gauges. The equipment should be maintained in proper working condition.
2. Paint ingredients should be kept uniformly mixed in spray pots or other containers
during painting and the paint should be continuously or intermittently mixed by
mechanical means.
3. Spray equipment should be kept clean. Dirt, dried paint or other foreign materials must
not be deposited in the paint film. Any solvents left in the equipment should be
completely before they are reused.
4. Paint should be applied in a uniform layer with a 50overlap on each pas. During
application, the paint gun should be held perpendicular to the surface and at a distance
which ensure that a uniform layer of paint is deposited on the surface. The gun's
trigger should be released at the end of each "stroke"
5. All runs and sags should be brushed out immediately or the coating should be
removed and the surface repainted.
6. Cracks, crevices, blind areas of all rivets and bolts and all other inaccessible areas
should be painted by brush.
7. The paint should be suitable for the particular spray application method used.
8. Particular attention should be given to thinner type and amount, paint temperature and
operating techniques to avoid applying paint that is too viscous, too dry or too thin. In
some cases, the paint may have to be thinned to suit the application method.
9. Caution must be exercised so that hot coatings are not applied on cold surfaces and
conversely, that cold coatings are not applied on hot surfaces.
FAULT |
PROBABLE CAUSE |
SUGGESTED CORRECTION |
Runs and sags |
Improper spray technique |
Only personnel (sprayers) who are familiar with airless application techniques should be used |
Gun is passed to close to surface |
Gun should be held at a distance of about 30 cm from the surface for general work |
Gun stroked at wrong angle to surface |
Gun should be stroked at the right correct angles |
Gun not triggered properly excess overlapping |
The spray pattern should overlap slightly and the gun should be triggered at surface interruptions |
Excessive deposit |
In addition to the above check spray nozzle for excessive wear or improper selection |
Excess dilution |
Each paint has a given viscosity and solids content below which it cannot be diluted and still hold the specified film thickness. Therefore, do not think the paint unless absolutely necessary |
Streaks
(rat tails) |
Wrong nozzle |
Select a smaller nozzle |
Nozzle is worked out or worn-out |
Use a new nozzle |
Incorrect overlapping of strokes |
Follow the previous stroke accurately. Deposit a wet coat |
Paint too cold |
Increase pressureheat paint |
Too high viscosity |
Increase pressurethin paint |
Too high film |
Improper technique |
See notes on "Runs and sags". Use a smaller nozzle. Hold the gun at the right annals to the application surface |
Dry over-spray |
Excessive atomization.
Nozzle too small.
Improper Technique |
Reduce pressure. Use a larger nozzle. Hold spray gun closer to the surface. Spray at right angles to the surface. |
Excessive spray fog |
Excessive atomization |
Reduce pressure |
Gun stroked too far from surface |
Stroke the gun about 30cm from the surface |
Paint thinned out too much |
Only the correct amount of thinner should be added to the paint |
Pinholes |
Paint film too heavy
Poor atomization |
Apply lesser wet film thickness. Increase pressure |
"Orange Peel" |
Paint not thinned sufficiently |
Add the correct amount of thinner |
Paint too cold |
Paint requires heating prior to application or use hot applicators |
Not building a wet coat |
Check that the correct thinner is used |
Blistering |
Rust, oil or grease on surface |
Degrease the surface properly before painting Remove rust Layer on surface by the appropriate means |
Moisture on or in surface |
Surface temperature must be above dew point Dry surface completely before application |
Solvents trapped under dried paint |
Use a solvent with a higher evaporation speed |
