A charging electrode at the nozzle runs at up to about 100 kV, ionizing the air so powder passing through picks up a negative charge. Corona guns work with nearly any powder, give high transfer efficiency on open surfaces and are easy to automate. The free ions they make cause Faraday cage problems in corners and back ionization when film gets thick, which is why gun controllers offer current limiting.
Corona gun's fine for the flat panels, but the boxes need the kV dialed down for the corners.
Also heard as
- corona charging gun
Do not mix it up with
- Tribo gun: A tribo gun charges powder by friction, with no high-voltage electrode and almost no free ions.
Related terms
Tribo gun
A powder gun that charges particles by rubbing them against a plastic tube, with no high-voltage electrode.
kV
Kilovolts, the voltage setting on a corona gun that governs how hard it charges the powder.
Free ions
Charged air molecules from a corona electrode that never attach to powder but still land on the part.
Back ionization
Tiny electrical discharges inside an overcharged powder layer that repel new powder and pit the finish.
Faraday cage effect
The tendency of charged powder to avoid inside corners and recesses because the electric field bunches on nearby edges.