Powder spray guns impart an electrostatic charge to powder particles as they pass through the spray gun on their way to the part. The gun controls allow varying gun position, velocity, shape of pattern, and charge levels to direct the powder’s deposition on the part. Powder spray guns are manual (handheld) and automatic (fixed mount), internal and external charging, corona charging with internal or external high-voltage supplies, and triboelectric (frictional charge). These variations have their advantages, their weaknesses, and their particular roles in painting parts. During electrostatic powder coating, the high-voltage potential applied to the tip of the gun’s charging electrode creates an electric field between the gun and grounded part. This leads to the development of corona discharge. A great number of free ions — generated by the corona discharge — fill the space between the gun and part. Powder particles capture some ions, thus charging the particles.
By Gary Conner
By George N Bullen FSME