Powder Coating Troubleshooting Guide

Chapter Thirteen: TCI Troubleshooting Guide

Appearance Issues


Problem	Origin	Solution

Craters	Contaminates in compressed air	Powder coating systems should have a ded-icated regenerative air dryer. Compressed air should be at 38°F dew point or lower. No particulates greater than 0.3 microns or oil greater than 0.1 ppm should be present.
	Powder material in-compatibility	Make sure the powder coating system is cleaned properly
	Air-born or foreign material incompatibility	Inspect area for possible contaminates such as silicone
	Poor pre-treatment	Check pre-treat equipment and concentrations
Pin-Holing	Contaminates in compressed air	Check system for compressed air contaminates
	Excessive Film Thickness	Decrease film build via voltage, powder delivery, or lessen time sprayed on part
	Excessive Oven Temperature	Reduce oven temperature and/or time in oven
	Substrate porosity	Check the substrate for surface porosity. If substrate is sand-blasted, check recommended blast profile
Color loss and poor opacity	Over-cured/ Under-cured	Run DataPaq oven profiler to confirm proper cure. The recommended time at metal temperature should be met
	Out-gassing and micro-pin holing	Check for moisture within compressed air and check the surface for porosity
	Contamination	Make sure coating area is free from airborne contaminates and confirm powders are compatible.
	Poor oven exhaust	Check that the oven has the correct amount of turn-overs and that the oven exhaust are working properly
Poor flow or too much orange peel	Film thickness too low (poor flow)	Increase film thickness via voltage or higher powder delivery
	Film thickness too high (orange peel)	Surface overcharged Back Ionization
	Powder too fine	Adjust virgin/reclaim ratio
	Oven temperature too high	Adjust temperature/time
	Coating not cured	Adjust temperature/time
Sagging	Film thickness too high	Decrease film thickness via voltage or lower powder delivery
	Too much powder sprayed on hot parts	Hot parts attract more powder, apply correct film build
	Oven temperature too low	Increase oven temperature and/or time
	Too much flow in powder	Contact TCI

Cured Film Properties


Problem	Origin	Solution

Poor adhesion	Coating under-cured	Run DataPaq oven profiler to confirm proper cure. The recommended time at metal temperature should be met
	Poor pre-treatment	Check pre-treat equipment and concentrations. Contact pretreat supplier
	Excessive film thickness (creates brittleness)	Decrease film build via voltage, powder delivery, or lessen time sprayed on part
Poor impact resistance and flexibility	Excessive film thickness	Decrease film build via voltage, powder delivery, or lessen time sprayed on part
	Poor-pretreatment	Check pre-treat equipment and concentrations
	Coating under-cured	Run DataPaq oven profiler to confirm proper cure. The recommended time at metal temperature should be met
Poor pencil hardness and abrasion resistance	Coating under-cured	Run DataPaq oven profiler to confirm proper cure. The recommended time at metal temperature should be met. Contact TCI representative
Poor corrosion resistance	Poor pre-treatment	Check pre-treat equipment and concentrations
	Coating under-cured	Run DataPaq oven profiler to confirm proper cure. The recommended time at metal temperature should be met

Application


Problem	Origin	Solution

Inconsistent powder delivery (guns are spitting and/or surging)	Blockage in spray gun, powder feed hose, or pump	1. Purge the spray gun. Remove the nozzle and electrode assembly and clean them. 2. Disconnect the powder feed hose from the spray gun and blow out the powder tube with an air gun. 3. Disconnect the powder feed hose from the pump and gun and blow out hose with an air gun. 4. Disassemble and clean the pump, replace venturi is worn.
	Damp powder	Check the powder supply, air filters, and air-dryer for moisture.
	Low pump air flow/pressure	Adjust pump air flow/pressure.
	Powder too fine	Adjust virgin/reclaim ratio.
	Poor powder fluidization	See "Hopper fluidization" section.
Powder repelling from parts (back ionization)	Voltage too high	Adjust voltage on controller, activate current limiting.
	Excessive film build	Apply the powder to powder vendor's recommended film build.
	Poor Ground	Check the conveyor chain, load bars, and drop-down hooks for powder build-up. The resistance between the parts and ground must be 1 Meg-Ohm or less.
Insufficient powder coverage (poor penetration in faradays)	Voltage too low or too high	Adjust voltage so coverage is even on edges and Faradays
	Powder/air velocity too high	Adjust air so the powder does not rebound from Faradays
	Poor Ground	Make sure part ground is below 1 Meg-Ohm
	Powder application technique or improper gun placement	Make sure spray technique and patterns are directed properly
	Powder too fine	Adjust virgin/reclaim ratio.
Poor powder charging (poor wrap and film build)	Poor voltage at gun tip	Measure voltage at gun tip with a kV ana-lyzer. If results are poor, replace electrode and test again. Replace gun/multiplier as needed.
	Poor ground	Make sure part ground is below 1 Meg-Ohm
	Powder too fine	Adjust virgin/reclaim ratio
	Humidity too low	Make sure paint room has a relative humidity in the 40% - 60% range

Hoses and Pumps


Problem	Origin	Solution

Pumps and hoses clogged from impact fusion	Build-up from routine maintenance not being performed	Clean and replace parts as needed. Start scheduled preventative maintenance
	Moisture in air supply	Make sure that air compressor and air drier are working properly
	Air pressures too high	Use lower air pressures on guns and powder transfer
	Powder too fine	Adjust virgin/reclaim ratio. Contact your local TCI service representative
Insufficient powder feed to application gun	Poor powder fluidization	See "Hopper fluidization" section.
	Obstruction in powder delivery hose	Check and clean the pumps, pick-up tubes, and powder delivery hoses. Make sure that the sieve screen is working properly and that no holes or tears are pre-sent. Make sure that the powder is not clump inside the hopper and that no foreign mate-rials are present.
	Powder delivery hoses kinked or crushed	Avoid sharp bends in powder hoses. Make sure hose length is not crushed under wheels, hoppers, or other equipment.
	Worn pump venturis	Check and rotate venturis daily. Throw out all venturis out of range and clean away impact fusion with non-metallic tools. Use an ultra-sonic machine for best results.
	Low air pressures	Check air delivery lines for kinks or obstructions. If none are found gently increase air supply to the feed pump.

Fluidized Hoppers


Problem	Origin	Solution

Powder escaping from feed hoppers	Excessive fluidizing pressure	Adjust fluidizing pressure so fluidized state is at a gentle roll.
	Poor hopper ventilation	Make sure that the hopper vent has a straight path and is not clogged. Adjust assist air accordingly

	Powder too fine	Use lower air pressures on guns and powder transfer or adjust virgin/reclaim ratio.
Poor Fluidization	Low air setting or im-proper air line size	Adjust air to properly fluidize. Make sure air line supply is of adequate size.
	Moist or clumpy powder in hopper	Feel bottom of hopper and make sure powder clumps are not present. If clumps are present contact powder supplier. Check air lines for moisture
	Fluidizing plate bad	Replace the fluidizing plate
Uneven deposition of fine and course powder particles inside the hopper	Virgin/reclaim mix poor	Adjust virgin/reclaim ratio. Anything under 20% fines should work reasonably well. Above 20% fines may cause issues. If powder reaches above 25% fines, the feed hopper should be run down and reloaded with virgin. If the powder reaches 40% fines it should be blended with virgin to raise the average particle size or it should be scrapped. Contact your local TCI Service Representative