Powder coating manufacturers and users are constantly exploring powder coating technology. Powder coating and its application technology are a rapidly developing new process and technology in my country over the past decade. It features energy and resource savings, reduced environmental pollution, simple processes, easy automation, durable coatings, and recyclable powder. Below is a summary of common problems encountered in powder coating application.
1. Paint Film Discoloration
1.1 Causes:
1.1.1 Residual treatment liquid on the coated surface;
1.1.2 Over-baking, or the presence of volatile gases in the oven;
1.1.3 Mixing in other colored powders during application;
1.1.4 The pigments in the powder coating itself are not heat-resistant, or the resin is prone to yellowing.
1.2 Solutions:
1.2.1 Improve pretreatment methods;
1.2.2 Establish appropriate baking conditions and clean the baking oven;
1.2.3 Strengthen pre-application cleaning;
1.2.4 Replace with qualified powder coating.
2. Particles/lumps on the coating surface
2.1 Causes:
2.1.1. The surface of the workpiece being coated is not clean;
2.1.2. Uneven powder supply, poor atomization by the spray gun;
2.1.3. Powder is too fine or the powder is damp and clumps together, causing powder accumulation in the spray gun;
2.1.4. The coating area is not clean or powder drips from the spray booth;
2.1.5. The quality of recycled powder or the powder coating itself is poor.
2.2 Solutions:
2.2.1. Improve the quality of the workpiece substrate and strengthen pretreatment;
2.2.2. Adjust the air pressure, check the air guide, and adjust it to the optimal point;
2.2.3. Control the powder particle size distribution, properly store the powder, and strictly prevent moisture absorption;
2.2.4. Clean the work area and purify the air;
2.2.5. After sieving the recycled powder, mix it with new powder for reuse, and replace with qualified powder.
3. Pinholes
3.1 Causes:
3.1.1. Oil stains on the workpiece surface;
3.1.2. Water, oil, etc., in the compressed air, causing powder contamination;
3.1.3. Contamination by dust or other impurities;
3.1.4. Contamination in the powder coating itself.
3.2 Solutions:
3.2.1. Strengthen pretreatment;
3.2.2. Strengthen the purification of compressed air before coating;
3.2.3. Thoroughly clean the environment and replace with qualified powder.
4. Poor Leveling or Severe Orange Peel
4.1 Causes:
4.1.1. Rough workpiece surface;
4.1.2. Coarse powder particles, dampness, or poor powder leveling;
4.1.3. Curing temperature too high or too low;
4.1.4. Coating film too thin or too thick;
4.1.5. Poor workpiece grounding;
6. Mixing of different powders.
4.2 Solutions:
4.2.1. Improve workpiece surface finish;
4.2.2. Select high-quality powder with uniform particle size distribution and good leveling properties, and strictly prevent powder from getting damp;
4.2.3. Adjust suitable curing conditions;
4.2.4. Control powder thickness to 60-80μm;
4.2.5. Clean the spraying fixtures regularly;
4.2.6. Thoroughly clean the powder spraying system and site before construction, and avoid mixing powders of different types or from different manufacturers.
5. Loss of Gloss on Coating Surface
5.1 Causes:
5.1.1. Poor substrate pretreatment quality;
5.1.2. Excessive baking time or temperature;
5.1.3. Presence of volatile gases in the oven;
5.1.4. Excessive use of recycled powder;
5.1.5. Mixing of two powders with different properties;
5.1.6. Poor quality powder coating.
5.2 Solutions:
5.2.1. Select a suitable pretreatment process;
5.2.2. Adjust appropriate curing conditions;
5.2.3. Clean the oven;
5.2.4. After filtering, mix the recycled powder with new powder, ideally keeping the ratio <30%;
5.2.5. Thoroughly clean the powder coating system before changing powder;
5.2.6. Replace with high-quality powder.
6. Coating film contains pores and pinholes
6.1 Causes:
6.1.1. Pores on the workpiece surface;
6.1.2. Residual treatment liquid on the workpiece surface, incomplete degreasing and rust prevention;
6.1.3. Conductive putty applied too thickly and not fully dried;
6.1.4. Spray gun too close to the workpiece, excessively high application voltage, causing coating breakdown;
6.1.5. Volatile gases in the drying tunnel;
6.1.6. Coating too thick, or the coating not fully cured;
6.1.7. Problems with the powder coating itself
6.2 Solutions:
6.2.1. Improve the processing of the workpiece;
6.2. 2. Improve pretreatment process;
6.2.3. Extend baking time;
6.2.4. Adjust process parameters;
6.2.5. Clean the drying tunnel and purify the oven gas;
6.2.6. Control the coating thickness to 50-80μm and adjust curing conditions;
6.2.7. Replace with qualified powder coating
7. Poor mechanical properties of the coating film, with the coating peeling off in large pieces
7.1 Causes:
7.1.1. Poor substrate quality, improper pretreatment method;
7.1.2. Improper baking conditions, incomplete curing or over-baking;
7.1.3. Poor powder quality, or expired powder.
7.2 Solutions:
7.2.1. Improve pretreatment;
7.2.2. Determine a suitable baking process;
7.2.3. Select qualified powder, and conduct a comprehensive inspection of expired powder.
8. Poor Corrosion Resistance of Coating
8.1 Causes:
8.1.1. Incomplete curing of the coating;
8.1.2. Uneven oven temperature with large temperature differences;
8.1.3. Improper workpiece preparation;
8.1.4. Poor performance of the powder coating
8.2 Solutions:
8.2.1. Adjust baking conditions according to coating performance;
8.2.2. Select a suitable oven with a temperature difference of ±5℃;
8.2.3. Strengthen pretreatment to avoid treatment solution residue on the workpiece surface;
8.2.4. Replace with qualified powder coating.
9. Poor Powder Adsorption and Flying
9.1 Causes:
9.1.1. Insufficient or no high voltage generated by the electrostatic generator;
9.1.2. Poor grounding of the workpiece;
9.1.3. Excessive air pressure;
9.1.4. Blockage in the air duct of the recovery device;
9.1.5. Incomplete pretreatment (rust, oil);
9.1.6. Problems with the powder coating itself.
9.2 Solutions:
9.2.1. Check the electrostatic generator and adjust the voltage;
9.2.2. Clean the mounting fixtures and ensure proper grounding; 9.2.3. Adjust air pressure;
9.2.4. Clean the recovery device;
9.2.5. Strengthen pretreatment process;
9.2.6. Use qualified powder coating
10. Uneven powder supply, inconsistent powder spraying
10.1 Causes:
10.1.1. Partial blockage in the powder pipe, poor powder flowability;
10.1.2. Insufficient air pressure, unstable pressure;
10.1.3. Oil and water mixed in the air;
10.1.4. Unstable fluidization of the powder feeder, insufficient powder supply.
10.2 Solutions:
10.2.1. Clean debris or clumps from the powder pipe, keep the powder pipe unobstructed, and adjust the dry powder flow;
10.2.2. Select a suitable air compressor;
10.2.3. Regularly remove oil and water from the air compressor;
10.2.4. Maintain stable fluidized bed air pressure and add fresh powder regularly.
