Don't panic when spray painting problems occur; finding the root cause will solve the problem.

During the spray painting process, defects such as particles, runs, and orange peel in the paint film are a major concern for many professionals—not only affecting the product's appearance but also potentially leading to rework and wasted costs. These problems are not without clues; most are related to process parameters, material selection, and equipment condition. This article compiles 12 of the most common spray painting defects, breaking down their underlying causes and providing practical solutions to help you quickly troubleshoot and accurately resolve issues, resulting in more stable spray painting effects.

1. Poor Atomization

Core characteristics: Uneven paint mist dispersion, appearing in lumps or threads, resulting in a rough and dull coating surface. Common Causes and Solutions:

1. Low atomizing air pressure → Increase atomizing air pressure promptly to enhance paint mist dispersion;

2. Excessive paint output → Reduce output or increase atomizing pressure to balance paint volume and dispersion;

3. High paint viscosity → Add appropriate thinner to reduce viscosity and make the paint mist finer;

4. Bent electrode needle at the nozzle tip → Carefully straighten the electrode needle; replace it if severely deformed;

5. Worn or damaged nozzle → Replace with a new nozzle to avoid atomization abnormalities due to nozzle issues;

6. Poor solvent compatibility → Communicate with the paint manufacturer promptly to replace with a compatible solvent.

2. Excessive Paint Rebound

Core Symptom: Excessive paint rebound during spraying, making it difficult to adhere to the workpiece surface and resulting in significant waste. Common Causes and Solutions:

Excessively High Atomization Pressure: Reduce atomization air pressure to decrease paint impact.

Excessively Long Spraying Distance: Control the spray distance to approximately 200mm to improve paint adhesion.

Insufficient Paint Resistance: Adjust the resistance value according to the paint instructions to enhance adhesion.

Poor Workpiece Grounding: Ensure the workpiece is fully grounded to eliminate rebound caused by electrostatic repulsion.

Insufficient Spray Booth Air Velocity:Increase the air velocity to promptly remove rebound paint mist and prevent secondary interference.

3. Low Paint Coverage

Core Manifestation: Low coating coverage after a single spray, requiring multiple touch-ups to achieve the desired result. Common Causes and Solutions:

1. Poor Workpiece Grounding → Check the grounding line to ensure complete grounding and enhance electrostatic adsorption;

2. Atomizing Air Pressure Too High → Appropriately reduce atomizing pressure to prevent paint from being blown away;

3. Spray Distance Too Large → Shorten the spray distance to approximately 200mm to improve paint utilization;

4. Setting Voltage Too Low → Increase the spraying voltage to enhance the paint's electrostatic adsorption capacity;

5. Paint Resistance Too High → Adjust the paint resistance to a reasonable range to optimize adsorption;

6. Spray Booth Wind Speed ​​Too High → Reduce the wind speed to prevent paint from being carried away by the airflow.

4. Filamentous Foreign Matter

Core Manifestation: Filamentous paint adheres to the nozzle, or filamentous foreign matter remains on the workpiece surface, affecting the smoothness of the coating.

Common Causes and Solutions:

1. Solvent Evaporation Too Fast → Replace with a paint with slower evaporation, or add a special additive to adjust;

2. Paint Viscosity Too High → Reduce paint viscosity to prevent the paint from forming filaments due to viscosity.

5. Spray Surface Particles

Core Manifestation: Fine particles are distributed on the paint film surface, resulting in a rough feel and damaging the appearance. Common Causes and Solutions:

1. Poor Atomization → Readjust atomization parameters to ensure fine paint mist;

2. Dust in the Spray Booth → Replace the dust filter and clean the workpiece surface before spraying;

3. Atomized Air Pollution → Clean or replace the air passage filter to ensure clean air source;

4. Poor Pigment Dispersion in Paint → Change to a suitable solvent or filter the paint.

6. Thin Paint Film

Core Manifestation: The coating is thin and cannot completely cover the base color of the workpiece, resulting in insufficient protection.

Common Causes and Solutions:

5. Insufficient Paint Output → Appropriately increase the paint output to increase the thickness of a single spray;

6. Paint Viscosity Too Low → Add a thickener to increase viscosity and prevent excessive paint flow that leads to thinning.

7. Heavy Orange Peel Texture

Core Manifestation: The paint film surface is uneven, resembling orange peel, with obvious blemishes or pits. Common Causes and Solutions:

Spray booth temperature too high or solvent evaporation too fast: Adjust the room temperature to a suitable range and replace with a slower-evaporating solvent.

Workpiece temperature too high: Lower the drying oven temperature and allow the workpiece to cool to room temperature before spraying.

Spray booth wind speed too high: Adjust the wind speed to 0.5-1.0 m/sec to balance paint mist flow and adhesion.

8. Spray Surface Sagging

Core Manifestation: Excessive paint flow in certain areas of the coating, resulting in defects such as tear marks and sagging.

Common Causes and Solutions:

Coating film too thick: Reduce paint output, increase spray gun speed, and control the thickness of each spray coat.

Paint viscosity too low: Increase paint viscosity to prevent excessive paint flow.

Slow solvent evaporation: Replace with a faster-evaporating paint to promote rapid drying.

9. Porosity

Core Manifestation:Pinpoint-sized pores on or inside the paint film, affecting density and protective properties. Common Causes and Solutions:

Air Pollution from Atomization:Clean or replace the air filter to ensure a clean air source.

Solvent Evaporation Too Fast:Use a slower-evaporating paint to prevent the paint film from drying too quickly and creating pores.

Workpiece Temperature Too High: Allow the workpiece to cool to a suitable temperature before spraying.

Insufficient Primer Drying: Extend the primer drying time to ensure complete curing before applying the topcoat.

10. White Spots

Core Manifestation: Irregular white spots appear on the paint film surface, often related to the environment or solvents.

Common Causes and Solutions:

High Temperature and Humidity in the Spray Booth: Use a slower-evaporating solvent and check the air conditioning equipment to adjust temperature and humidity.

Unsuitable Solvent: Communicate with the paint manufacturer to replace with a compatible solvent.

11. Blistering

Core Manifestation: Localized bulging of the paint film forms bubbles, which may rupture and peel off in severe cases, resulting in loss of protective function. Common Causes and Solutions:

Air Contamination: Clean or replace the air filter to ensure the air source is free of impurities.

Insufficient Drying After Washing: Extend the drying time to ensure the workpiece surface is completely dry.

Excessively Thick Paint Film: Reduce the paint output to control coating thickness.

Excessively Fast Solvent Evaporation: Use a slower-evaporating paint to prevent solvent buildup within the paint film.

Excessively High Drying Oven Temperature: Adjust the drying oven temperature to the paint's suitable range.

12. Poor Spray Pattern

Core Symptom: The spray pattern is skewed and inconsistent in width, resulting in uneven coverage of the workpiece surface.

Common Causes and Solutions:

Paint Adhesion at the Air Cap or Paint Outlet: Thoroughly clean the air cap and nozzle to remove residual paint.

High Paint Viscosity: Reduce paint viscosity and optimize paint mist flow.

Damaged Nozzle: Replace the nozzle to ensure a regular spray pattern.

Incorrect Spray Pattern Adjustment: Readjust the spray pattern control knob to calibrate the spray pattern.

Improper Nozzle Installation: Disassemble and reinstall the nozzle and air cap, ensuring proper installation.

13. Summary

The root causes of poor coating results are mostly concentrated in four dimensions: equipment status, process parameters, material compatibility, and environmental conditions. The key to solving these problems is to first observe the defects, then investigate possible causes, and finally take precise countermeasures. For example, regarding paint mist issues, prioritize adjusting atomization pressure and paint viscosity; for adhesion issues, focus on checking grounding, spray distance, and voltage; for surface defects, pay attention to environmental cleanliness, solvent compatibility, and drying conditions.

In daily production, it is recommended to perform regular equipment maintenance (cleaning nozzles, checking filters), record process parameters (voltage, spray distance, air velocity), and verify material compatibility (paint and solvent matching). This can effectively reduce the occurrence of defects. For complex problems, timely communication with the paint manufacturer is crucial to avoid blind adjustments that could lead to further problems. Mastering these troubleshooting techniques can significantly reduce the coating defect rate and ensure more stable coating quality.