The Electrostatic Charge

The electrostatic powder coating process is a method of applying electrically-charged powder coating materials to grounded parts. Powder is held to the part by this electrostatic attraction until heat is added to flow the powder together and cure it.

There are four basic pieces of equipment that commonly make up an electrostatic powder spray coating system. They are the powder feeder, power unit, electrostatic gun, and powder booth recovery system.

To start, the powder is supplied to the spray gun from a feeder unit where the powder is circulated by compressed air into a free-flowing state. The fluidized powder is then funneled out by high velocity air and is propelled through the powder feed tubing to the spray gun.

The powder then leaves the spray gun in a diffused cloud being pushed toward the workpiece. At the front of the spray gun, a high-voltage, low-amperage power unit supplies a charging electrode, which emits a charge that is passed onto the powder particles. This causes the particles to attach themselves to the grounded workpiece.

Electrostatic attraction of powder at the substrate surface:

• Powder will retain a charge for several hours (minimally) if grounded properly. 
• As the powder contacts a grounded surface, it induces an equal and opposite charge on the surface of the substrate. 
• This occurs because like ions are repelled from the area. This reaction is called a “mirror” charge and serves to hold the powder particle in place.
• Larger particles typically have stronger charges, therefore larger particles will tend to build on top of smaller particles more directly on the surface. 

For more information like this, please see or download our powder coating technical guide on our website.