7 Common Powder Coating Defects and How to Prevent Them

Most powder coating defects are predictable – and preventable. They usually trace back to pretreatment, film build, or gun settings. Here are the seven most common problems we see, what causes them, and how to stop them before they cost you a re-run.

1. Orange Peel

Cause: the film does not flow out level enough before curing – often from low film thickness, low atomizing pressure, gun distance too far, or a cure temperature too low. Prevention: keep the film in the recommended range, tune the gun (voltage, air pressure, distance), and check the oven reaches the metal temperature, not just the air temperature.

2. Pinholes and Outgassing

Cause: gas or moisture escaping from the substrate during cure, common on castings, porous metal and surfaces with trapped moisture. Prevention: pre-heat parts to drive out gas before coating, and make sure the pretreatment and drying oven fully remove moisture. A primer coat can seal porous castings.

3. Poor Adhesion

Cause: contamination, oil, rust or an unsuitable conversion coating under the film. Prevention: proper degreasing, blasting or phosphating before coating, and checking the part is clean and dry before it enters the booth. Adhesion should be verified with a cross-cut test on the first parts of every run.

4. Runs and Sags

Cause: film thickness above the flow-out capacity of the powder, usually on vertical faces or near holes and edges. Prevention: reduce powder output or increase gun speed, and keep the target thickness inside the data sheet range. Some formulations with better flow can mask the issue, but thickness control is the real fix.

5. Color Variation

Cause: different pigment loads between batches, uneven film thickness, or inconsistent cure. Metallic powders are especially sensitive. Prevention: control color against the approved sample with a spectrophotometer, keep film thickness uniform, and retain batch samples so any drift can be traced quickly.

6. Faraday Cage Effect

Cause: the electrostatic charge cannot reach recessed corners and inside angles, leaving thin or bare areas. Prevention: reduce gun voltage and distance for recesses, use a shorter spray distance with lower air, or angle the gun to direct charged particles into the cavity. Pretreatment quality also helps the thin film still adhere.

7. Dirt and Fiber Contamination

Cause: dust, fibers and shop debris settling on the part before or during spraying, then becoming embedded in the film. Prevention: keep the booth under slight positive pressure with good filtration, clean parts before coating, and inspect the first parts of every run under good light before curing.

How We Help You Avoid Defects

Every order leaves our factory with tested film thickness, adhesion, gloss and color against the approved sample, and we include the Certificate of Analysis with the shipment. If a defect appears on your line, our engineers work with you to trace it to pretreatment, application or cure – because a defect caught early is much cheaper than a re-run.