When the electrostatic spray gun, spray plate, or spray cup is working, the paint particles are connected to the negative electrode, and the workpiece is connected to the positive electrode and grounded. Under the action of high voltage from the high-voltage power supply, the spray gun (or spray plate, or spray cup) An electrostatic field is formed between the end of the tool and the workpiece. The electric field force experienced by the paint particles is directly proportional to the voltage of the electrostatic field and the charge of the paint particles, and inversely proportional to the distance between the spray gun and the workpiece. When the voltage is high enough, an air ionization zone is formed near the end of the spray gun, and the air becomes intense. The ground is ionized and heated, forming a dark red halo around the sharp edge of the end of the spray gun or the pole needle, which can be clearly seen in the dark. At this time, the air produces a strong corona discharge.
Most of the film-forming substances in coatings, namely resins and pigments, are composed of polymer organic compounds, mostly conductive dielectrics. In addition to film-forming substances, solvent-based coatings also include organic solvents, co-solvents, Curing agents, electrostatic thinners, and other various additives and other substances. In addition to benzene, xylene, solvent gasoline, etc., most of these solvent substances are polar substances with low resistivity and certain conductivity. They can improve the charging performance of the paint.
The molecular structure of dielectrics can be divided into two types: polar molecules and non-polar molecules. Dielectrics composed of polar molecules show electrical properties when subjected to an external electric field; dielectrics composed of non-polar molecules are better outside.
The paint is sprayed out after being atomized by the nozzle. The atomized paint particles are charged due to contact when they pass through the pole needle at the muzzle or the edge of the spray plate or spray cup. When the particles are generated by corona discharge As the gas ionizes, its surface charge density will again increase. Under the action of the electrostatic field, these negatively charged paint particles move towards the polar workpiece surface and are deposited on the workpiece surface to form a uniform coating film.