Adjust film thickness to recommended range. Consult your Diamond Vogel® Technical Service Representative.
Lower the voltage settings on the equipment.
Some powder coatings are formulated and manufactured to tighter, more controlled particle size distribution allowing for a smoother film.
Clean feed and spray systems completely before color changes (cross contamination).
Dedicated powder hoses (and feed hoppers) can reduce the chance of contamination.
Off Color Film
Examine application procedures to determine if variations in film thickness are causing the problem.
Evaluate time at peak metal temperature, to determine if the parts have been over cured.
Check oven exhaust.
If the powder is off color, please contact your Diamond Vogel® Technical Service Representative.
When applying a semi-gloss or flat coating and it appears that the gloss is too high after coming out of the oven, check oven settings and part temperatures. This is usually an indication of under cured powder.
Check oven and part temperatures to determine if the part has been over cured.
Always make sure powder coatings are compatible before mixing.
Check for microscopic pinholing or outgassing (see section 17).
Variations in Film Thickness
Check application patterns and gun set-ups.
Could be caused by surges in the powder flow (see section 8).
Turbulence in the booth air flow.
Usually caused by air or moisture being trapped in porous metal or castings.
Pre-heat parts before applying powder, or bake at a slower rate.
Use powder coatings that are formulated to be more forgiving for outgassing.
Edge Pull, Craters
Poor surface preparation can cause voids and craters in a coating.
Excessive phosphate residues on edges can create edge pull.
Check dry-off oven for residual moisture on parts.
Extremely smooth powder coatings may exhibit more edge pull due to the flow of the coating.
Increase voltage settings for more edge coverage.
Poor Hardness and Abrasion Resistance
Always know part temperatures and times to avoid under curing the coating. Either increase the oven temperature or extend the time in the oven.
See "Determining Cure through the Solvent Rub Test."
Poor Corrosion Resistance
Check your pretreatment system for cleaning effectiveness. Evaluate phosphate coating weights along with total dissolved solids levels in rinse tanks.
Evaluate total film thickness to determine most effective level for the end environment.
Always know peak metal temperatures and total time at that temperature to avoid under curing the coating.
Lack of Flexibility and Adhesion
Usually caused by under curing.
Check pretreatment system for cleaning effectiveness. Evaluate phosphate coating weights along with total dissolved solids level in rinse tank.
Check for excessive total film thickness.
Color Shift in Metallics
Changes in gun to part distance and voltages will change the orientation of the metal flake within the coating, causing color shift.
Increasing the KV may darken color.
Decreasing the distance may darken color.
Increasing the distance may lighten color.
Decreasing the KV may lighten color.
Changes in the powder delivery rate and total film thickness will also affect color. Control both factors.
Dry blended powders may stratify.
Higher metallic concentrations can lead to short circuits in powder delivery system.
Frequently purge the gun with air to maintain a clean tip.