Troubleshooting Guide

powder coating troubleshooting guide

1.POWDER APPLICATION    2.CURED FILM DEFFECTS
3.MECHANICAL &CHEMICAL PROPERTY
1.1.Thin Film (Substrates show through and coating layer has grainy flow)
       Possible Causes Solutions
       High humidity powder Control environment
Ensure all powders are kept sealed until required to use
       Poor charging Increase voltage
Clean or replace electrodes,cables,etc if needed
Decrease powder delivery rate
       Poor grounding Use clean hooks; Check and improve grounding
       Poor deposition rate Increase powder delivery air;Reduce line speed
       Faraday cage effect Adjust voltage and forward air flow
1.2.Poor Fluidization (Poor fluidization causes slow and no transportation of powder from fluid container to guns)
       Possible Causes Solutions
       Fluidizing air too low or too high Change air pressure; Use large hose diameter
       Oil remnants in compressed air Check filter in front of coating booth
       Damp or compact powder Manually loosen powder in hopper
1.3.Poor Penetration in Faraday areas
       Possible Causes Solutions
       Voltage not optimized Reduce voltage,so that surfaces closest to the gun do not repel powder
       Powder delivery rate
not optimized
Adjust delivery rate
       Poor part ground Check and improve grounding
       Incorrect powder spray pattern Try different spray nozzle
       Poor gun placement Adjust gun position
       Poor part presentation Improve part presentation
       Powder too fine Reduce ratio of reclaim to hopper
1.4.Back Ionization (Surface looks uneven and broken before curing )
      Possible Causes Solutions
      Gun voltage too high Reduce voltage
      Gun too close to part Increase the distance between gun and part
      Poor part grounding Check and improve the grounding
      Excessive powder build-up Spray thinner film
      Moisture powder Ensure no moisture is entering the system
1.5.Powder Surging or Spitting
      Possible Causes Solutions
      Not optimized powder
delivery rate
Optimize powder delivery rate
      Incorrect hose diameter Uses smaller diameter hose
      Improper air pressure Optimize air pressure
      Clogged worn parts,tubes or hoses Check and clean or replace worn parts as needed
      Moisture in compressed air Ensure clean dry air
      Much more fines powder Add virgin powder
1.6.Much Thicker Film(layer shows uneven surface before curing,orange peel or pinholes will show after curing
      Possible Causes Solutions
      Excessive powder delivery Reduce powder feed to gun
Increase distance between gun and component
      Curing time too long Shorten curing time
      Gun voltage too high Adjust voltage
      Too much pre-heat(if exists) Reduce pre-heat cycle
2.CURED FILM DEFFECTS
2.1.Pinholes In the Filem(Fine pores on the surface,also can leads to change in gloss )
      Possible Causes Solutions 
      Inadequate cleaning of substrate Check cleaning and phosphating
      Silicone,oil Contaminatants Check source and eliminate,check degreasing plant
      Oil in compressed air supply Ensure clean ,dry air supply
      Moisture content in powder
too high
Testing through drying of powder
      Very porous workpiece Check for satisfactory workpieces,maybe no enough sandblasting
2.2.Picture Framing(Higher film build-in on the edges of part due to wrap,uneven flow)
      Possible Cause Solutions 
      Excessive film thickness Reduce film thickness
      Poor part grounding Check and improve grounding
      Voltage too high Adjust voltage to suit
      Feed air or powder flow too high Adjust powder flow
2.3.Outgassing or blistering
      Possible Cause Solutions 
      Excessive film thickness Check system parameter,reduce film thickness
      Cast or other porous substrate De-gas at or above cure temperature
      Water on workpiece Check dryer and hanging configuration
      Liquid paint under powder Remove pain,de-gas at or above cure temperature
2.4.Orange Peel(Poor flow,short or long waviness of coating layer,shown after curing)
      Possible Causes Solutions 
      Heat up cycle of part too slow Increse  heat up rate
      Improper film thickness Check system parameter and adjust film thickness
      Incompatibility with other powder Clean booth,check compatibility
      Voltage too high Optimize voltage
      Substrate profile Increase film thickness or change substrate
      Powder Stored at or
exposed to elevated temperature
Replace powder
Store powder at or below recommended temp.
      Unsuitable particle zise distribution Optimize particle size distribution
2.5.Low Gloss
      Possible Causes Solutions
      Oven temperature too high Redue temperature,and check metal temperature,or increase line speed
      Time in oven too long Increase line speed;decrease oven temp.
      Contamination with a powder Clean all equipment including gun,booth,recovery system
2.6.High Gloss
      Undercured coating flim Increase curing time or temperature
      Slow heat up cycle Increase cure temperature;preheat substrate
2.7.Poor Adhesion
      Undercured film Increase oven temperature;decrease line speed
      Poor pre-treatment Check pre-treatment
2.8.Contamination of colos
      Possible Causes Solutions
      Poor cleaning when
color changing
Clean plant,gun and recycling system
      Cross contamination
at manufacturer
Contact powder supplier
      Contamination from
equipment cleaning
Vacuuming is more effective
      Desposits from dust and
particle in oven
Donot cure other color at same time; reduce air speed
2.9.Off-color or yellowing
      Possible Causes Solutions
      Overbaking Reduce curing time or temperature
Increse line speed
Check burner locations to eliminate hot spots
      Line stoppages Eliminate line stoppages or reduce oven temp.during stoppages
Leave gaps to provide for scheduled line stoppages
     Inadequate oven exhaust Increase oven exhaust rate or reduce line loading
1.POWDER APPLICATION 2.CURED FILM DEFFECTS