During work, the electrostatic spray gun or spray and spray cup parts are connected to the negative electrode, and the workpiece is connected to the positive electrode and grounded. Under the high voltage of the high voltage electrostatic generator, the end of the spray gun (or spray plate, spray cup) forms with the workpiece An electrostatic field. The electric field force on the coating particles is proportional to the voltage of the electrostatic field and the charge of the coating particles, and is 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. The intense ionization and heat generated a dark red halo around the sharp edge of the end of the spray gun or around the pole needle, which can be clearly seen in the dark. At this time, the air generates a strong corona discharge.
Most of the film-forming materials in coatings, such as resins and pigments, are composed of high-molecular organic compounds, which are mostly conductive dielectrics. Solvent-based coatings include organic solvents, co-solvents, curing agents, electrostatic diluents, And other various additives.
Except for benzene, xylene, solvent gasoline, etc., these solvent substances are mostly polar substances, have low resistivity, and have a certain electrical conductivity. They can improve the charging performance of coatings. The molecular structure of a dielectric can be divided into polar molecules and non-polar molecules. A dielectric composed of polar molecules exhibits electrical properties when subjected to an external electric field; a dielectric composed of non-polar molecules exhibits electrical polarity under an applied electric field, thereby generating affinity for external conductive charges, which causes the dielectric to be applied externally. The outer surface of the electric field can be locally charged.
The paint is sprayed after being atomized by the nozzle, and the atomized paint particles pass through the pole needle of the muzzle or the edge of the spray plate, and the edge of the spray cup, and are charged due to contact. When passing through the ionization zone of the gas generated by the corona discharge, it will recharge. Increase its surface charge density once. The electrostatic field of these negatively-charged paint particles moves to the surface of the polar workpiece and is deposited on the surface of the workpiece to form a uniform coating film.