TCI Application & Troubleshooting Guide

Chapter Thirteen: Coating Application Troubleshooting

Pre-Treatment
     
Problem Origin Solution

Parts are dirty after cleaning.

 

 

 

 

 

Soils are not being removed.

 

 

 

 

 

Check to ensure that all soils are identified.

Test all stages. Determine if the proper choice of chemicals and process conditions have been chosen; acid conditions clean inorganic soils and alkaline conditions clean organic soils.

Orient parts for maximum coverage.

Clean and adjust spray nozzles and spray pressure for maximum part coverage.

Maintain high rinse tank water purity.

  Temperature too low for cleaning soils. Increase operating temperature.
  Chemical concentrations are too low. Increase chemical concentrations.

Cross stage contamination.

 

Part geometry is not optimized and the part density is too high.

 

Configure parts for maximum cleaning and rinse coverage.

Allow sufficient time for adequate rinse and drainage between stages.

Little or no coating adhesion to part.

 

 

Soils are not being removed.

 

 

Check to enure that all soils have been identified. Test all stages. Determine if the proper choice of chemical and process conditions have been chosen.

Orient parts for maximum coverage. Clean. Adjust spray nozzles and spray pressure for maximum part coverage. Maintain high rinse tank purity.

Pretreated part appears with streaks or spots.

 

Soils are not being removed.

 



Test cleaning stage. Determine if the proper choice of chemicals and process conditions have been chosen; acid conditions clean inorganic soils, alkaline cleans organic.
 

Parts are not fully rinsed or rinse is contaminated.

Orient parts for maximum coverage. Clean and adjust spray nozzles for maximum coverage. Maintain high rinse tank purity.
  Dry off is occurring between stages.

Allow sufficient time for adequate drainage but not dry off between stages. Reduce temperatures. Utilize fog nozzles and adjust nozzles for maximum coverage.
 

Phosphate coating weight is too low.

Adjust processing conditions, such as increase temperature and lengthen time. Increase phosphate and/or accelerator concentration.

A powder is on the surface of the phosphate coated part.

Parts are not fully rinsed or the rinse is contaminated.

Orient parts for maximum coverage. Clean and adjust spray nozzles for maximum coverage. Maintain high rinse tank purity.
  Sludge is being transferred. Precipitate and filter sludge from the cleaning stage.
  The accelerator concentration is too high. Reduce the accelerator concentration.
Parts are rusting.

Phosphate coating weights too low.

Adjust processing conditions, such as increase temperature and lengthen time. Increase phosphate and/or accelerator concentration.
  Surfactants and soils remain, limiting phosphate disposition.

Adjust clean and rinse stages. Orient parts for maximum coverage. Clean and adjust spray nozzles for maximum part coverage. Maintain high rinse tank purity.
     
Application
     
Problem Origin Solution
Parts are rusting Dry off is occurring between stages. Allow sufficient time for adequate drainage but not dry off between stages. Reduce temperatures. Utilize fog nozzles and adjust nozzles for maximum coverage.
  Final dry off is too slow. Increase dry off oven temperature.
Solutions are foaming. Stage temperature is too low. Increase stage temperature.
  Line pressures are too high. Check for plugged nozzles. Adjust pressure if necessary.
  Air is being introduced. Check water levels. Check pumps for leaks.
  Improper chemical selection. Select foaming characteristics to match agitation and pressure levels to control excessive foaming.
Little or no adhesion on cured powder coating part. Phosphate coating weight is too low. Increase phosphate and/or accelerator concentration, process, time and temperature.
  Phosphate coating weight is too high. Reduce phosphate and/or accelerator concentration and process time.
  Surfactants and soils remain limiting the phosphate disposition. Adjust cleaning and rinse stages. Orient parts for maximum coverage. Clean and adjust spray nozzles for maximum part coverage. Maintain high rinse tank water purity
  Unidentified soils remain in the metal and/or process. Check to ensure all metal and process soils have been identified.
Inadequate film buildup or coverage due to poor charging. Powder delivery rate is too high to adequately charge the powder. Reduce powder delivery rate until the powder is sufficiently charged. Adjust spray gun positioning.
  Voltage to the charging electrode is too low. Assess the electrical continuity through out the electrostatic system. Clean or repair voltage limiting components.
  The part is not grounded enough for film build. Check contact areas to ensure there is no buildup of cured powder coating grease or any other insulating material which would impede ground.
  During application, the powder coating passes the part. Adjust and optimize spray gun positioning and air flow rates.
  Excessive moisture or oil in the air supply, the fluidized bed and/or powder booth. Humid air acts as an antistat. Monitor and control the humidity in the booth and the air supply.
  Excessive moisture in the powder coating. Moisture acts as an antistat. Store powder in a controlled environment.
  Powder coating may contain excessive concentrations of small size particles. Sustain a constant ratio of virgin powder and reclaimed powder. Monitor the particle size of the powder. Virgin powder may contain excessive fines. Contact TCI.
  Powder composition. Coating may be formulated only for a specific application. Contact TCI.
  Powder may not tribo charge.

Some powders have the ability to charge by friction others do not. Contact TCI.

Ensure tribo tube is not coated with powder particles limiting the creation of friction.

The powder will not penetrate a Faraday cage. Powder delivery rate is too low for adequate coverage. Increase powder delivery rate and air flow until the powder coverage is sufficient. Adjust spray gun position.
  During application, air velocity is too high and the powder blows out of corners. Adjust and optimize spray gun positioning and reduce air flow rates.
  High voltage creates a strong magnetic field obstructing penetration. Reduce voltage to the electrical field limiting penetration.
  The part is not grounded enough for powder penetration and film build. Check contact areas to ensure there is no buildup of cured coating, grease or other insulating material that impedes ground continuity.
  Incorrect spray pattern and gun placement. Reset guns to ideal nozzle selection, pattern setting and positioning to coat recessed areas.
Charged powder coating particles limit further disposition onto a surface. The part is not grounded adequately creating a surface charge repelling powder. Check contact areas to enure there is no buildup of cured coating, grease or other insulating material that impedes ground continuity. Avoid heavy powder buildup.
  High voltage creating a strong magnetic field. Reduce voltage to the electrical field to eliminate electrostatic rejection.
  A gun too close to a part will create a strong magnetic field. Increase the distance between the gun and part.
The powder is surging or spitting during application. Spray environment gun settings are not optimized. Too high humidity has a detrimental effect on application. Adjust environmental conditions for best application. Check hoses, pumps and guns for blockage. Make sure air supply is sufficient for good air volume.
  The powder flow is not continuous causing spitting. Check for good fluidization in hopper transfer areas. Check the porosity of the fluidization membrane. Adjust the air flow rates for optimum fluidization transfer and sustain sufficient powder levels.
Coating Properties and Appearance
     
Problem Origin Solution
Coating color drifts from the standard. Oven air is not exchanged enough to eliminate combustion by products. Adjust the air exchange rate to reduce the concentration of by-products. With light colors the oven volume must be exchanged several times more often than with dark colors to minimize discoloration and haze.
  The oven temperature may be too high. Reduce oven temperature. Know oven profile and set temperature and dwell to match cure schedule. Find hot spots in the oven. If an infrared oven is used vary the energy density and the line speed.
  The coating formulation may not have sufficient pigment opacity Increase coating thickness to provide coverage. Contact TCI for coverage requirements.
  Film thickness may be too thick or thin. The pigment opacity dictates the required thickness for proper color. Adjust for proper coverage. This is most predominant in metallic finishes.
The cured film has poor adhesion. Unsatisfactory cleaning and / or pre-treatment. Assess conditions and chemicals of the cleaning, rinse and pretreatment stages.
  A change has been made in the sub- strate without making changes to the process. Contact substrate suppliers to find out if any changes to the substrate have been made.
  Under cured films will exhibit low adhesion. Modify cure conditions by increasing temperature and dwell.
The film has poor chemical resistance. Under curing of the film. Systems vary in chemical resistance properties. Modify cure conditions by increasing temperature and dwell. Contact TCI for information and recommendations.
The coating has low flexibility and impact resistance. A change has been made in the substrate without making changes in the process. Contact suppliers to ensure no changes to the substrate have been made.
  The film thickness may be too thick. Reduce film thickness to TCI specs.
  Under cured films will have low flexibility. Modify cure conditions by increasing temperature and/or dwell.
The cured film has poor corrosion resistance. Unsatisfactory cleaning and/or pretreatment. Assess conditions and chemicals of the cleaning, rinse and pretreatment stages.
The film has poor hardness Under cured films will exhibit low hardness. Modify cure conditions by increasing temperature or dwell.
  Systems vary in hardness. Contact TCI for information and recommendations.
The film displays too much orange peel. Coatings vary in amount of orange peel properties. Contact TCI for information and recommendations.
  The film thickness may be too thick or thin. Increase or decrease the film’s thickness according to information.
Pinholes form in the surface of the coating. Coating is contaminated by an incompatible powder. Clean application equipment when changing from one powder to thenext.
  Pinholes produced from out-gassing. Determine the metal porosity. Adjust processing to minimize the affects of the metal porosity.

Adjust dry off oven temperature to ensure no moisture is on the part. Check powder for moisture introduced in reclaim, from the air supply or the virgin powder.

A thick film may cause out-gassing. Reduce the film thickness to enable the gas to escape through the surface during cure.

Urethane powder coatings may emit a blocking agent. Pinholes may occur in the surface at film build above 3 mils.

Pinholes are forming in the coating surface. Pinholes are produced from out-gassing. Excessively high cure temperatures may volatilize lower polymeric components within the coating. Note oven temperatures if pinholes form.
  Unsatisfactory rinse stages. Chemical from cleaning and pre-treatment stages may be dried onto the surface, volatilizing at higher cure temperatures. Assess conditions of rinse stages.
  Pinholes produced from vapors in the curing oven. Masking products are often plasticized to make the product soft and flexible. Plasticizers can evolve vapors that may reduce the coating’s hardness and produce pinholes. Monitor ovens and maintain appropriate air exchange.
Gloss is higher than the standard. Under cured films will exhibit variability in their gloss. Modify cure conditions by increasing temperature and/or dwell.
  The gloss of certain coating systems may vary with cure conditions. Contact TCI for information and recommendations.
Gloss is lower than the standard. The gloss of certain coating systems may vary with cure conditions. Contact TCI for information and recommendations.
  Pinholes will reduce the gloss. See problems with pinholes section.

 

Contact us today to speak with our experienced team about how we can help you with your powder coating needs.