Common Issues and Solutions When Applying Powder Coatings
One. Paint film discoloration
Causes:
1、The coated surface has residual treatment solution.
2、Overbaking or presence of volatile gases in the oven.
3. Other colored powders are mixed in during construction.
4、The pigments in the powder itself are not heat-resistant, or the resin may discolor.
Solution:
1、Improved pre-treatment methods.
2. Establish appropriate baking conditions and purify the baking oven.
3. Enhance pre-construction cleaning.
4、Replace with qualified powder coatings.
Two. The coated surface has granular lumps.
Possible causes:
1、The surface of the coated workpiece is not clean.
2、Uneven feed, poor atomization from the spray gun.
3、If the powder is too fine or the powder has absorbed moisture and clumped, it will clog the spray gun.
4、The spraying area is dirty or there are powder particles falling in the spraying room.
5、The recycled powder or powder itself is of poor quality.
Solution:
1、Improve the quality of the base material and enhance pre-treatment.
2. Adjust air pressure, inspect the drip edge, and set it to the optimal position.
3. Control the powder particle size distribution, store the powder properly, and prevent moisture absorption.
4. Clean the site and purify the air.
5、After screening the recycled powder, mix it with new powder, replacing it with qualified powder.
III. Cracking
Causes:
1、Cracking of the paint layer on the wall results in cracks on the wall surface. The primary causes include substandard paint quality.
2. Caused by improper operations during the application of wall paint.
3. Low temperatures prevent the wall coating from forming a continuous film, leading to cracking because the coating's film-forming temperature is not met.
Solution:
If the cracking is limited to the surface paint film, you can remove the cracks with fine sandpaper and then repaint the wall with the same color paint.
Four. Significant differences in leveling or severe orange peel effect.
Causes:
1、The surface of the fabricated component is rough.
2. The particle size is coarse, the putty powder is damp, or the putty powder has poor flowability.
3、The curing temperature is too high or too low.
4、The coating is too thin or too thick.
5. The workpiece is not properly grounded.
6、Mixing different powders.
Solutions:
1. Enhance the smoothness of the finished product.
2. Select high-quality powders with uniform particle size distribution and excellent flowability, and ensure that the powders are protected from moisture.
3. Adjust the appropriate curing conditions.
4. Control the powder thickness to be between 60-80μm.
5. Regularly clean hanging fixtures.
6. Before construction, thoroughly clean the spray system and the site, to prevent the mixing of different types or different brands of powders.
Five. Coating surface appears dull.
Possible causes:
1、The quality of substrate preparation is poor.
2、 Excessive baking time or excessively high temperature.
3、The furnace contains volatile gases.
4、The proportion of recycled powder used is too high.
5、Mixing two powders with different properties.
6、The quality of the powder coating is poor.
Solution:
1、Choose an appropriate pre-treatment process.
2. Adjust the appropriate curing conditions.
3. Clean the curing oven.
4、After filtering the recycled powder, mix it with new powder, with a ratio of no more than <30% recommended.
5、Before replacing the putty powder, thoroughly clean the spraying system.
6、Replace with high-quality powder.
Six. Coating exhibits air pockets and pinholes.
Possible causes:
1、The surface of the component has air pockets.
2、The surface of the work piece has residual cleaning agent, and the degreasing and anti-corrosion treatments are incomplete.
3、The conductive putty was applied too thickly and had not dried properly.
4、The spray gun was too close to the workpiece, resulting in excessively high voltage and coating penetration.
5、The duct contains volatile gases.
6、The coating is too thick, or the coating film has not fully cured.
7、Potential issues with the powder coating itself
Solution:
1、Enhance the processing of the components.
2. Improve the pre-treatment process.
3. Extend the curing time.
4、Adjust process parameters.
5、Clean the drying chamber and purify the gases inside the furnace.
6. Control the coating thickness to 50-80μm and adjust the curing conditions.
7. Replace with qualified powder coating.
Seven. The coating has poor mechanical properties and the entire coating detaches.
Causes:
1、Poor substrate quality and improper pre-treatment methods.
2. Improper baking conditions, resulting in incomplete curing or over-baking.
3. The powder quality is poor, or it has exceeded its expiration date.
Solution:
1、Improve pre-treatment.
2. Determine the appropriate baking process.
3. Select qualified powders; expired materials must undergo thorough inspection.
Eight. Poor corrosion resistance of the coating.
Possible causes:
1、The coating has not fully cured.
2、Uneven baking oven temperature, with a large temperature difference.
3. Improper handling of the work piece.
4、Powder coatings exhibit poor performance.
Solution:
1、Adjust the curing conditions according to the properties of the coating.
2. Select an appropriate oven with a temperature difference of ±5℃ between the upper and lower temperatures.
3. Enhance pre-treatment to prevent treatment solution from remaining on the workpiece surface.
4、Replace with qualified powder coating.
Nine. Poor dust absorption and adhesion.
Possible causes:
1、The electrostatic generator does not generate high voltage or produces insufficient voltage.
2、Poor grounding of the workpiece.
3、Excessive pressure.
4、Blocked airflow in the recovery device.
5、Incomplete surface treatment（For example：Rust、Grease）。
6、Problems inherent in the powder coating itself.
Solution:
1. Inspect the static electricity generator and adjust the voltage.
2. Remove hanging fixtures and ensure proper grounding.
3. Adjust air pressure.
4. Clean the recycling equipment.
5. Enhance pre-treatment processes.
6. Use certified powder coatings.
Ten. Uneven powder supply resulting in inconsistent powder spraying volumes.
Possible causes:
1、Partial blockage of the powder pipe, resulting in poor powder flow.
2、Insufficient air pressure, and unstable pressure.
3、The air contains oil and water.
4、The flow of the hopper is unstable, and the amount of powder dispensed from the hopper is insufficient.
Solution:
1、Remove any debris or clogs from the powder tube, ensuring the powder tube remains clear. Adjust the flowability of the dry powder coating.
2. Select the appropriate air compressor.
3. Regularly remove oil and water from the air compressor.
4. Maintain stable fluidized bed pressure and periodically add fresh powder.
Eleven. Pores reduction
Possible causes:
1、The surface of the fabricated item has oil stains.
2. The putty powder is contaminated with water, oil, or other substances present in compressed air.
3. Contaminated by dust or other debris.
4、The powder coating itself is contaminated.
Solution:
1. Enhance pre-treatment.
2. Enhance the air quality for spraying powder coatings by compressing air before application.
3. Thoroughly clean the work area and replace with qualified putty powder.