Powder Coatings Troubleshooting

Trouble

Causes

Solutions

1.Poor charging - inadequate powder build or wrap on part

1.High voltage source not providing enough KV at charging electrode or grid

1a. Check high voltage source is on. Systematically check electrical continuity from voltage source to electrode(grid) including cable resistors and fuses1

1b. Replace missing or broken electrode (grid). 1

1c. Clean electrode (grid) insulated by powder build or impact fusion. 1

2.Poor ground

2.Check ground from conveyor rail (or hub bar when used) through hanger to part. All contract areas must be free of powder build, heavy grease and other insulation materials

3.Powder delivery (feed) is too high

3.Turn down powder feed until all material passing through charging corona (field) is adequately charged

4.Excessive moisture in powder booth air

4.Moisture in humid air will tend to dissipate the charge on the powder particles. Control the humidity in the powder spray area. See chart for optimum conditions.

5.Powder too fine

5a.Too much reclaim added to virgin powder

5b.Virgin powder pulverised too fine by manufacturer

6.Powder type or formula

6.Some resin types charge better than others and some formulas are designed for thin film application. Check with your powder supplier

7.Powder delivery air too high

7.Turn down air setting or move gun position further away from part

2. Poor penetration – powder will not coat Faraday Cage area (holes, grooves, channels, inside corners and recesses)

1. Powder delivery too low

1a. Turn up powder delivery air setting

1b. Use gun barrel extension.

2. Poor ground

2. Check ground. See powder delivery, poor charging section, No. 2

3. Powder spray pattern too wide

3. Select smaller deflector or use suitable slotted barrel end cover. Consult your equipment supplier

4. Voltage too high

4. Turn voltage setting down so powder build on part edges and leading surfaces does not repel powder from corners

5. Powder delivery velocity

5. Turn air settings down so powder/air stream does not blow powder out of corners

6. Poor gun placement

6. Adjust gun position so powder cloud has a direct path to recess area

3. Back charging – powder layers are repelled from part in spots

1. Voltage too high

2. Gun positioned too close to part

3. Poor ground

1. Turn down voltage setting.

2. Change gun placement further away from part

3. Check ground. See powder delivery, charging section, No. 2

4. Tribo charging – powder picks up a random charge through powder hoses. Reverse charging usually through reclaim system

1. Powder booth air too dry

2. Poor delivery and/or reclaim equipment ground

1. Adjust powder spray area humidity. See chart for optimum conditions.

2. Provide ground for all equipment¹

5. Powder feed spurting or slugging – interrupted powder feed

1. Insufficient air pressure or volume

1a. Check air supply. Air supply piping to equipment is large enough. Enough air volume when other equipment such as reverse air cleaning in reclaim housing pulses, air pressure to powder feed does not drop

2. Hoses, kinked, flattened or too long

3. Hoses, pump venturies or guns clogged with powder

2. Check powder feed hoses. See hose section, insufficient feed No. 2

3a. Clean hoses, venturies and guns¹

3b. Check air supply for moisture that causes powder compaction.

3c. Check powder free flowing properties

3d. Check spray booth air humidity. See chart for optimum condition

6. Poor spray pattern – not a symmetrical powder cloud (not applicable when using special deflectors for desired effect)

1. Worn electrostatic gun parts

2. Impact fusion build

3. Delivery (feed) air too low

4. Hoses, venturies or gun blocked with powder

1. Replace worn feed tubes, orifices, deflectors and covers¹

2. Check gun parts as needed¹

3. Check air supply. Increase air for powder feed

4. Clean hoses, venturies and guns¹

Trouble

Causes

Solutions

1. Dusting - Powder blowing out of hopper

1.Air pressure too high

1.Adjust air regulator to lower pressure to fluid bed

2.Powder too fine

2a.Too much reclaim added to virgin powder

2b.Virgin powder pulverised too fine by manufacturer

2.No air - percolating through powder surface

1.Insufficient air pressure

1a.Check air supply. Increase air regulator pressure

1b.Check air line size to equipment

2.Plugged membrane

2.Check membrane for plugged pores from dirty air supply

3.Obstructed membrane

3.Check bottom of bed for plastic, cardboard or other large obstructions

4.Compacted powder

4.Manually loosen powder and fluidize well with clean air, dry

3.Rat holing - air blowing large jet holes powder surface

1.Powder level too low

1.Add powder until hopper is2/3 full when fluidised

2.Packed or moist powder

2a.Manually loosen powder and fluidize well with clean, dry air

2bCheck compressed air and booth air for high humidity

3.Membrane obstructed

3.Check bottom of bed for plastics, cardboard or other large obstructions

4.Plugged or broken membrane

4.Check membrane for plugged pores from dirty air supply cracks or holes.

4.Stratification - powder separating into layers of fines and coarse particles

1.Powder level high

1.Remove powder until 2/3 full when fluidised

2.Powder too fine

2a.Too much reclaim added to virgin powder

2b.Virgin powder pulverised too fine by manufacturer

Trouble

Causes

Solutions

1.Plugged from fusion - hard build up

1.Normal build up

1.Clean or replace parts 1

2.Air pressure too high

2.Turn down air settings on pumps and guns

3.Moisture in air supply

3.Check air supply for clean dry air,

4.Composition of powder feed hoses

4.Check hoses. 1

5.Worn venturies and wear parts

5.Replace worn parts. 1

6.Powder too fine

6a.Too much reclaim added to virgin powder

6b. Virgin powder pulverised too fine by manufacturer

7.Powder type or formula

7.Some resin types tend to have more impact fusion Check with your powder supplier

2.Insufficient powder feed

1.Powder not fluidizing

1.See fluidize bed section.

2.Obstruction from contaminated powder supply

2a.Clean out venturies and hoses

2b.Check powder supply for contamination

2c.Sieve all reclaim before using.

3.Kinked or flattened hoses

3a. Replace if permanently deformed

3b.Avoid sharp bends. Use hose saddles for reciprocators

3c.Run hoses in covered trenches across traffic aisles

4.Worn pump venturies

4.Replace worn parts 1

5.Low air pressure

5.Check air supply. Adjust air settings to pumps and guns

Trouble

Causes

Solutions

1. Contamination in reclaim powder

1.  Reclaim in-line sieve torn, missing or inoperable

2.  Powder or dirt falling in spray booth from conveyor or hangers

3.  Contamination from parts entering spray

 4. Contamination from plan air circulated through spray booth

1.  Replace sieve or repair necessary

2.  Clean conveyor regularly (or continuously) before entering powder spray booth. Strip hangers as needed

3.  Check cleaning and pretreatment equipment and ensure proper part draining before spray booth

4.  Isolate spray booth area. Preferably enclose in a room with filtered, humidity controlled air

2. Spray booth dusting – inadequate air flow through spray booth

1. Bag or cartridge filters binding

1a. Clean or replace bags or cartridge filters¹

1b. Check spray booth air humidity. See chart for optimum conditions

1c. Check reverse air cleaning

2. Final filters clogged

2. Check filter bags or cartridges for powder leakage. Repair or replace as needed¹

3. Too large of open area in spray booth housing

4. Powder delivery (feed) too high

3. Reduce open area. Increased opening reduces booth air velocity¹

4. Reduce the number of guns spraying or the amount of powder to each gun

Trouble

Causes

Solutions

1. Poor impact resistance/poor flexibility

1. Under cured

2. Poor cleaning or pretreatment

3. Film thickness too high

4. Change in substrate thickness or type

5. Powder resin type or formula

1a. Increase oven temperature

(or)

1b. Increase dwell time in oven

2. Check pretreatment equipment and chemicals¹

3. Reduce film thickness by adjusting application equipment¹

4. Check substrate with supplier

5. Check with powder manufacturer

2. Poor adhesion

1. Poor cleaning or pretreatment

2. Change in substrate

3. Under cured

4. Powder resin type or formula

1. Check pretreatment equipment and chemicals

2. Check substrate with supplier

3a. Increase oven temperature

(or)

3b. Increase dwell time in oven

4. Check with powder manufacturer

3. Poor corrosion resistance

1. Poor cleaning or pretreatment

2. Under cured

1. Check pretreatment equipment and chemicals¹

2a. Increase oven temperature

(or)

2b. Increase dwell time in oven

4. Poor chemical resistance

1. Under cured

1a. Increase oven temperature

(or)

1b. Increase dwell time in oven

2. Powder resin type or formula

2. Check the powder manufacturer

5. Poor pencil hardness/poor abrasion resistance

1. Under cured

2. Powder resin type or formula

1a. Increase oven temperature

(or)

1b. Increase dwell time in oven

2. Check with powder manufacturer