1.1 Poor Fluidisation in powder hopper
Powder is supposed to flow like water in the fluid container. Poor fluidization is recognizable in slow and non- continuous transportation of the powder to the guns. No homogenous powder Cloud is achieved.
| Possible Causes | Explanation |
| Powder level too low | Add powder to correct level |
| Fluidizing air too low or too high | Change pressure |
| Oil remnants in compressed air | Use larger hose diameter Check filter |
| Compact or damp powder | Manually loosen powder in hopper |
| Fluidizing plate clogged/defective | Clean plate or renew |
| Powder contains too much fines | Check if enough fresh powder is in circuit |
1.2 Clogging of the powder feed hoses
Deposits form in the powder feed hoses, which sporadically are freed by delivery air and appear as powder puffs on the work pieces. After curing these powder puffs appear as faulty surface elevations.
| Possible Causes | Explanation |
| Feed air pressure too high/low | Reduce/increase pressure |
| Delivery air moist or oil in pressurized air | Cheek in-line filters and moisture traps |
| Material choice of hoses | Check hoses for material quality |
| Worn venture or pump | Replace worn parts |
| Too fine powder | Decrease amount of reclaim to hopper Optimize virgin powder ratio |
| feed hose too long | Minimize feed hose length |
1.3 Poor attraction of powder to the components
The powder coating which should electrostatically adhere to the substrate, falls off – no relevant coating thick- ness can be achieved.
| Possible Causes | Explanation |
| Incorrect voltage at the gun | Check voltage, dean or replace gun |
| Insufficient grounding | Clean grounding points and hangers |
| Excessive build-up of cured powder | Clean hangers |
| Worn out venture or pump | Replace worn parts |
| Too much powder output | Reduce Air flow |
| Gun distance to part too close, blast effect | Adjust the distance |
| Gun air pressure too high | Reduce forward air pressure |
| Film built too high | Reduce powder flow |
| Insufficient wetting | Check pretreatment |
1.4 Poor Wrapping
With one sided gun positioning only minimal film thickness can be achieved on opposite side.
| Possible Causes | Explanation |
| Powder flow too low or high | Optimize system parameters, adjust air flow |
| Insufficient grounding | Use clean hooks |
| Supplemental air flow is too high or low | Adjust air speed and powder cloud |
| Gun voltage too high | Adjust voltage to suit parts |
| Insufficient charging of the powder | Adjust high voltage, consult powder supplier |
| Poor or wrong positioning of the parts | Adjust hanging configuration |
1 .5 Poor penetration into recesses
Despite the physical condition it is possible to achieve a minimum coating thickness in the corners. Extreme film thickness variation are noticeable.
| Possible Causes | Explanation |
| Too low powder delivery | Increase powder flow |
| Air speed too high | Adjust equipment controls |
| Powder flow too high | Adjust equipment controls to suit parts |
| Poor grounding | Check and improve grounding |
| Insufficient charging of the powder | Adjust voltage, consult powder supplier |
| Incorrect spray pattern | Try different spray nozzles |
| Too high voltage | Reduce voltage, so that surface closest to the gun do not repel powder |
| Poor gun placement | Reduce voltage, so that surface closest to the gun do not repel powder |
| Powder too fine | Reduce ration of reclaim to hopper. contact powder supplier |
1.6 Film thickness on component too high
Powder coat layer shows uneven surface prior to curing, after curing shows orange peel or pinholes
| Possible Causes | Explanation |
| Excessive powder delivery |
|
| Coating time too long | Lower the coaling time/increase line speed |
| Unfavorable geometry of parts | Change hanging or gun configuration |
| Gun voltage too high | Reset gun voltage |
| Too much pre-heat (if used) | Reduce pre-heating |
1.7 Film thickness on component too low
Substrate shows through and powder coat has grainy flow
| Possible Causes | Explanation |
| Powder delivery too low |
|
| Coating time too short | Increase time by reducing line speed |
| Insufficient charging of powder | Adjust voltage |
| Faraday cage effect | Adjust voltage and forward air flow |
| Surface area of hanger too large compared to the
surface area of work piece |
Reduce size of hangers |
| Damp powder | Remove powder and replace. Ensure all powder coatings are kept sealed until required in use |
| Insufficient grounding | Use clean hooks, avoid thin hooks |
| Low level of powder in fluid hopper | Check minimum indicator |
1.8 Appearance looks uneven and broken before curing
| Possible Causes | Explanation |
| Back ionisation |
|
1.9 Insufficient wet out of the substrate
| Possible causes | Explanation |
| Too high air pressure | Reduce air pressure to fluid bed |
| Too fine powder |
|
2.1 Powder puffs on the work piece
Powder puffs are clusters that in an improperly fused condition are visible as powder hills in the powder film. After curing these powder puffs appear as disturbing elevations on the surface
| Possible causes | Explanation |
| Powder hose too long or diameter too Large | Change hose diameter, shorten hose |
| Powder too fine | Add virgin powder |
| Powder falls off booth ceiling | Adjust frequency of booth cleaning |
| Powder falls of work piece | Test grounding, check diameter of hoses |
| Fluidizing plate clogged / defective | Clean plate or renew |
| Powder contains too much fines | Check if enough fresh powder is in circuit |
2.2 Craters
Defect – blank area in the powder coat, which extends all the way to the substrate
| possible Causes | Explanation |
| Insufficient pre-treatment (oil and grease) | Test pre-treatment especially the last rinse |
| Rust | Assure clean surfaces |
| Finger prints | Do not touch pre-treated material |
| incompatibility with other powders | Clean the facility, contact powder supplier |
| Work piece moist/Wet | Increase drying time |
| Liquid and powder paint in the same area | Definitely avoid – reconfigure plant |
| Base coat was cleaned with solvent | Preheat work piece and avoid solvents |
| Silicone contamination | Locate and remove source |
2 .3 Pinholes
Fine pores on the surface. also leads to change in gloss level
| possible Causes | Explanation |
| Silicone contamination | Locate and remove source |
| Oil contamination | Check degreasing plant |
| Moisture content of powder too high | Check oil/water separators on air supply |
| Film build too high | Minimize film thickness (Primid powders are very critical to that) |
| Very porous work pieces | Check for satisfactory work pieces, possible surface is too rough from sand blasting. |
| Incompatibility with other powders | Clean the facility, contact powder supplier |
2.4 Picture framing effect
Higher film build of coating on the edges of the part due to wrap, therefore uneven flow.
| possible Causes | Explanation |
| Voltage too high | Adjust voltage |
| Distance between gun and part to short | Adjust distance |
| Feed air/powder flow to high | Adjust powder flow |
2.5 Contamination of color
Points of olni.lr colors appear in the surface.
| possible Causes | Explanation |
| Poor housekeeping, when colour changing | Totally clean plant |
| Cross contamination at manufacture | Contact powder supplier |
| Contamination from equipment cleaning | Vacuuming is more effective than air |
| Deposits of dust and particles in ire oven |
|
| Deposits of dust and powder on cured object | Adjust voltage: consult powder supplier |
2.6 Blistering
Elevations of different size in the powder coal, no adhesion due to enclosures at the paint surface.
| Possible Causes | Explanation |
| Water on work piece | Check and adjust dryer |
| Water residues in complicated shapes | Optimize hangers |
| Residues of oil grease and rust | Optimize pre-treatment |
| Salt residues or chemical remnant on | Check pre-treatment, final rinse zone |
2.7 Poor Adhesion
| Possible Causes | Explanation |
| Under cure film |
|
| Poor pre-treatment | Check pre-treatment |
2.8 Orange peel
Poor flow, short or long waviness of powder coat layer, noticeable only alter curing
| Possible Causes | Explanation |
| Heat up cycle of parts too slow | Determine heat up curve and increase |
| Substrate temperature exceeds the melt temperature of the powder | Check substrate temperature |
| Powder coaling material too reactive | Consult supplier |
| Film thickness to high or low | Check system parameters |
| incompatibility with other powder | Clean booth, check compatibility |
| Voltage too high | Optimize voltage |
| Textured work piece surface | Optimize texture, check work piece surface |
| Unsuitable particle size distribution | Optimize particle size |
2.9 Insufficient wet out of the substrate
Poor or no adhesion of powder coat to the parts surface, large area lifting of cured powder coat.
| Possible Causes | Explanation |
| Pre-treatment residues | Final rinse de-ionised water |
| Displaced oils or greases in pre-treatment excessive film build | Pre-treatment, check oil separator |
| Gummed oils, greases or separating compounds insoluble extrusion oils | Check pre-treatment |
2.10 Gloss too high
| Possible Causes | Explanation |
| Cure temperature too low |
|
| Oven cycle too shod |
|
2.11 Gloss too low
| Possible Causes | Explanation |
| Cure temperature too high |
|
| Oven cycle too short |
|
| Contamination with a powder which is incompatible | Clean all equipment |