Only a small share of the ions a corona electrode creates attach to powder particles. The rest travel to the grounded part, piling charge onto the powder layer without adding any coating. Free ions drive back ionization and strengthen the field at edges, making Faraday areas harder to coat. Ion collectors, current limiting and lower kV cut the free-ion load.
That's free ions building up, the film stops growing at two mils no matter how long you spray.
Also heard as
- free ion current
Related terms
Corona gun
A powder gun that charges particles with a high-voltage electrode at the tip, the most common gun type.
Back ionization
Tiny electrical discharges inside an overcharged powder layer that repel new powder and pit the finish.
kV
Kilovolts, the voltage setting on a corona gun that governs how hard it charges the powder.
Faraday cage effect
The tendency of charged powder to avoid inside corners and recesses because the electric field bunches on nearby edges.