Powder Coating Troubleshooting

When you run into problems on your application line it can be very difficult to get your powder supplier to help you unless you give the informations below correctly;


- What exactly is the problem?
- What products, lot number and box number are you using?
- Did you try another lot or box?
- Does this happen with all powders or just this one?
- What are your curing conditions?
- How are the parts pretreated?

Poor fluidization
Powder coating has poor fluidization in powder hopper. Powder is supposed to flow like liquid in the hopper. Poor fluidization is recognizable in slow and non-continous transportation of the powder coating in hopper. As a result no homogenous powder film thickness is achieved.
Causes Solutions
Powder level is low in hopper Add fresh powder
Fluidizing air too low or too high adjust air pressure

Fluidizing plate defected Celan or exchange the plate
Fresh powder has poor fluidization Add fluidizaiton addive to powder (contact with your supplier)

Poor attraction
The powder coating has poor attraction to the substrate. The powder coating should electrostatically adhere to the substrate. Othervise it falls off and no proper coating thickness can be achieved.
Causes Solutions
Insufficient grounding clean grounding points and hangers
Incorrrect voltage at the gun Check voltage by device, repair or replace a new one
Too much powder flow to substrate reduce air flow
Gun distance to part too close or too farAdjust the distance 20-30 cm
Insufficient charging of the powder increase the voltage or contact with your supplier
Inappropriate positioning of the parts adjust hanging configuration

Poor penetration
Because of faraday cage effect it is possible to achieve low film thickness in the corners.
Causes Solutions
Insufficient grounding clean grounding points and hangers
Incorrrect voltage at the gun Check voltage by device, repair or replace a new one
Too high voltage reduce voltage
Incorrect spray nozzle try different spray nozzle
Poor gun placement adjust gun position to enter directly into corner

High film thickness
After curing, the film thickness is high.
Causes Solutions
Too high voltage reduce voltage
Excessive powder spray reduce porder feed to gun
Coating time too high increase conveyor speed
Too much pre-heat (if used) reduce preheat temperature

Low film thickness
After curing, the film thickness is low.
Causes Solutions
Insufficient grounding clean grounding points and hangers
Insufficient powder spray set correct powder feed to gun
Insufficient coating time decrease conveyor speed
Faraday cage effect read poor penetration problem
Insufficient powder in hopper Add fresh powder
Inappropriate positioning of the parts adjust hanging configuration
percentage of overspray too high add more fresh powder or reduce overspray powder
Using non Tribo powders in Tribo systems Use tribo powder
Gun-to-part distance too high Reduce distance
Plugged transport system Clean the transport system regularly

Back ionization
Powder is repelled from part in spots. It can occur when the part being coated becomes saturated with free ions, resulting in nowhere for the charge particles to go put back the way it came.
Causes Solutions
Too high voltage reduce voltage
Insufficient grounding clean grounding points and hangers
High film thickness reduce film thickness
Gun distance to part too close Move gun away from substrate

Dusting out of cabinet
Dusting of powder comes out of application cabinet.
Causes Solutions
Insufficient grounding clean grounding points and hangers
Excessive powder spray reduce porder feed to gun
Inappropriate application cabinet Reduce gun amount, increase air suction rate
Too fine powder reduce overspray powder, check ratio of fresh powder

Agglomerates (sintered powder)
The powder coating is lumping in powder box. If the clumps can be easily broken up the powder form should still be usable.
Causes Solutions
Inappropriate storage Store the powder cool and dry area.
Glass transition temperature Tg of contact with your supplier
powder coating is low

Craters
Crater is a surface defect. It is blank area in the powder coat.
Causes Solutions
Inappropriate pretreatment check the parameters of pretreatment. Apply the same powder onto untreated panel
Rust on parts apply proper pretreatment, sandblast surface
Oil in feed or atomizing air Check in-line filters and moisture traps in air system
Silicones from anywhere never use product that contains silicone
Incompatibility with powder coatings clean all application equipments and start with fresh powder
Outgassing from substrate Preheat substrate and use proper powder coating for degassing
Substrate is wet increase drying time or temperature
Liquid and powder coating in same plant avoid coming close them