How Charged Powder Particles Coat a Grounded Part
Electrostatic spraying is the core application method for powder coating. It works in the following stages:
Key Takeaways
- Powder picks up a negative charge at the gun, typically 60-100 kV, by corona or friction charging.
- The grounded part attracts the charged cloud, and the electric field bends into recesses and around edges.
- The charge holds the powder on the part before curing, so there is nothing to sag or drip like wet paint.
- Overspray keeps its charge and can be collected and reused, which is where the 90%+ material utilization comes from.
1. Charging the Powder
As powder particles pass through the spray gun nozzle, a high-voltage electrode (typically 60–100 kV) gives each particle a negative electrostatic charge, either by corona charging (particles pass through an ion field) or friction / tribo charging (particles rub against a Teflon-lined tube and pick up charge that way).
2. The Charged Cloud Leaves the Gun
The powder exits as a charged cloud rather than a simple stream, since like-charged particles naturally repel each other and spread out.
3. The Grounded Part Acts Like a Magnet
The metal workpiece is electrically grounded, so it’s at a much lower potential than the charged powder. The electric field between the gun and the part pulls the negatively charged particles toward the grounded surface.
4. Wraparound Effect
This is the key advantage over liquid paint: the electric field lines curve around edges and even partially onto the back side of the part, so charged particles get pulled into recesses and corners a straight spray wouldn’t reach.
5. Electrostatic Cling
Once a particle lands, its charge holds it in place against gravity and airflow, which is why the powder stays put even before curing — there is no wet paint to sag or drip.
6. Overspray Recovery
Powder that misses the part is still charged, so much of it can be recovered and reused (typical for booth reclaim systems), unlike liquid overspray.
Summary
The whole trick is basically: charge the powder, ground the part, and let the electric field do the aiming.
Frequently Asked Questions
How does powder stick to the part before it is cured?
Each particle carries an electrostatic charge and the part is grounded, so the powder clings to the surface by electrostatic attraction until the oven melts and cross-links it.
What is the wraparound effect in powder coating?
Electric field lines curve around edges and partially onto the back of a part, so charged particles reach recesses and corners that a straight spray would miss.
Can oversprayed powder be reused?
Yes. Powder that misses the part stays charged and can be recovered by the booth reclaim system and blended back, unlike liquid paint overspray.
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