Corona vs tribo charging: which powder coating gun should you choose?
The two charging methods behave differently on the same part. Here is where each one wins, and how to decide with a trial instead of a catalogue.
Every electrostatic powder coating gun charges powder by one of two methods. The difference is not a feature you can add later — it is baked into the gun’s electrode design, and it changes which parts you can coat well.
How each method charges powder
Corona charging uses a high-voltage electrode (typically 60–100 kV) at the gun tip. A corona discharge ionises the air around the electrode, and powder particles pick up charge as they pass through it. Charge is applied from outside the particle and is relatively high, which means strong deposition and good transfer efficiency on flat work.
Tribo charging has no external electrode. Powder particles rub against the inside of a PTFE or similar barrel and pick up charge by friction. The charge is lower, but it sits closer to the particle surface and is not driven by an external field.
Where corona wins
- Flat sheets, panels, simple extrusions, and anything with an open face toward the gun.
- High line speeds where you need maximum deposition per pass.
- Heavier film builds in a single coat.
- Most general job-shop work. This is why corona is the default.
Where tribo wins
- Recesses and inner corners. This is the headline benefit. Corona’s strong external field sprays ions that partially neutralise the charged powder inside a recess, so the powder simply does not go in.
- Tube interiors and box sections, where the gun can reach but the field cannot.
- Re-coat and touch-up areas, because there is no field to repel powder from already-coated regions.
Corona has a partial fix: reduce voltage and current, increase gun-to-part distance, and use a Faraday-cage or “tribo-like” nozzle attachment. It helps, it does not solve it.
The Faraday cage problem
If your parts have deep channels, unvented corners or tubular sections, you have a Faraday cage problem. Symptoms are characteristic: good coverage everywhere except the deep areas, and a film that comes out thin and rough exactly where the geometry hides.
If more than a small share of your parts look like that, the decision is normally tribo for those parts — not more voltage.
How to decide
| Your part profile | Charging choice |
|---|---|
| Panels, extrusions, flat or simple shapes | Corona |
| Mixed job shop, mostly open geometry | Corona |
| Deep recesses, tubes, box sections | Tribo, or corona with reduced settings |
| Re-coat-heavy work | Tribo |
| High-speed automatic line, simple parts | Corona |
Do a trial, do not assume
The honest answer is that this is decided by trial on your actual parts. Ask any supplier for a test spray on your three hardest geometries — deep recess, tube interior, and a standard flat panel — and inspect film thickness at the recess, not on the face.
A gun that wins on the flat panel and loses 30 µm in the recess is the wrong gun for that product, regardless of what the specification sheet implies.