When we apply powder coating, we want a perfect finish: smooth, resistant, and uniform. However, sometimes small defects appear that ruin the final result. One of the most common defects is pin-hole.
What is pin-hole?
Pin-hole is a defect where tiny holes or micro-bubbles appear on the painted surface after curing. They look like very small dots or pin-sized holes. Even though they seem minor, they can cause problems with corrosion and durability, since they allow moisture to enter the metal over time.
Why does pin-hole happen?
Pin-holes are usually caused by air or gases trapped under the paint, which try to escape during the curing process. The most common causes are:
| Cause | Description |
| Oil or grease on the part | Cutting oil, lubricants, fingerprints |
| Moisture | Water trapped after washing |
| Poor degreasing | Incomplete cleaning before painting |
| Porous welds | Gases released from inside bad welds |
| Contaminated parts | Dust, silicone, or aerosols |
| Incorrect curing | Low temperature or not enough curing time |
| Painting hot metal | Forces air out and causes bubbles |
How to prevent pin-hole in powder coating
The good news is that pin-hole can be prevented with a good process. Here are some practical tips:
✅ 1. Clean properly
Before painting, make sure the part is completely clean and free of oil or grease. The best option is to use a biodegradable industrial degreaser like SERVEC 1, which also improves paint adhesion.
✅ 2. Rinse well
After washing, rinse the part to remove all chemical residues. Any residue can cause defects.
✅ 3. Dry completely
Do not paint if the part is still wet. Moisture causes pin-holes. Dry especially well in corners or tubes.
✅ 4. Fix welding issues
Check if welds have porosity. Poor welds trap gas that escapes during curing and causes pin-hole.
✅ 5. Control oven temperature
Make sure the oven reaches the correct metal temperature and curing time (typically 180°C / 356°F for 10 minutes metal temperature).
✅ 6. Avoid contamination
Do not use silicone sprays or oils near the painting area. Keep surfaces free of dust.
Can pin-hole be repaired?
Yes. If it appears after curing, you can sand the area (grit 320–400), clean it, and repaint. In production, an anti-gassing primer is sometimes used to prevent recurring issues on porous metals.
Conclusion
Pin-hole seems like a small problem, but it affects product quality and durability. The best way to avoid it is by following a proper surface preparation process and good painting control.
✅ Clean
✅ Rinse
✅ Dry
✅ Control curing
✅ Use quality products
A well-prepared surface means a perfect powder coating finish.