Electrostatic spray application uses a fluidized bed as a feed hopper to
hold the powder and fluidize it so that it can be pumped to the tip of a
spray gun using compressed air for transport from the feed hopper to
the gun tip.
The spray gun is designed to impart an electrostatic charge
to the powder material and direct it toward a grounded workpiece.
This process makes it possible to apply much thinner coatings with a
wide variety of decorative and protective features.
The electrostatic charge can be imparted with voltage, called corona
charging, or by frictional contact with the inside of the gun barrel,
called tribo charging.
In a corona charging system, a voltage source generates current through a voltage cable that carries it to the powder gun tip. Powder is pumped through the gun and out of the gun tip using compressed air. As the powder passes through the electrostatic field at the gun tip, it picks up a charge and is attracted to a grounded substrate. The part is then conveyed into an oven for curing of the powder. In the cure oven, the powder melts and cross-links to a hard film to complete the process.
Electrostatic spray application of powder is the most common application method. The parts to be coated are cleaned, dried, and cooled, the coating is applied and cured at the required temperature for the required time and then cooled for removal from the line.
An electrostatic spray application system includes a delivery system
and a charging system.