Electrostatic spraying gun
Posted by: doPowder | on June 5, 2012
The term electrostatics or electrostatic spray finishing refers to a spray finishing process in which electrical charges and electric fields are used to attract particles of atomized coating material to the target (the object to be coated). In the most common types of electrostatic systems, electrical charges are applied to the coating material and the target is grounded, creating an electric field. The charged particles of coating material are drawn by the electric field to the surface of the grounded target because of the attraction of opposing electrical charges.
Electrostatic spray charging improves the transfer efficiency of spray finishing equipment. The transfer efficiency improvements occur because the electrostatic forces help overcome other forces, such as momentum and air flow that can cause the atomized materials to miss the intended target.
An electrostatic spray application system includes a delivery system and a charging system. It uses a fluidized bed as a feed hopper to fluidize the powder and use the compressed air to pumpe to the spray gun tip.
The spray gun is designed to generate an electrostatic charge to the powders and direct it to a grounded work piece. This process makes it possible to apply much thinner coatings with various decorative and protective features.The electrostatic charge can be generated with voltage, called tribo charging,by frictional contact with the inside of the gun barrel, or the other called corona charging.
In a corona charging system, a high voltage generator is used to charge an electrode at the tip of the powder gun. This creates an electrostatic field (or corona) between the gun and the substrate. Gas molecules in the air pick up electrons emitted from the corona. This negative charge is, in turn, transferred to the powder particles as they are propelled from the gun head towards the substrate. The charged powder particles are deposited on the earthed substrate.
Electrostatic spraying gun system has been the most popular coating methods for powder coating powder.