Electrostatic spraying is a coating method that uses the corona discharge phenomenon to charge the atomized paint under the action of a high-voltage DC electric field and adsorb it on the surface of the substrate to discharge.
Electrostatic spraying principle | fundamental | Electric field formation | The coating particles of the electrostatic spray gun are connected to the negative electrode, and the workpiece part is connected to the positive electrode and grounded. Under the influence of the high voltage power supply, an electric field is formed between the tail end of the nozzle and the workpiece. |
Coating charged | Under the action of electric field, the coating particles field force and the electrostatic field voltage and the coating particles charged, and inversely proportional to the nozzle and the distance between the workpiece, when the voltage is high enough, the nozzle area near the end form air ionization zone, air intense ionization and heating, make the nozzle end sharp edge or needle around a dark red halo, can be clearly seen in the dark, then the air produce strong corona discharge. | ||
Coating adsorption | The negatively charged coating particles under the electrostatic field, guide the polar workpiece surface movement, and are deposited on the workpiece surface to form a uniform coating film. | ||
technical parameter | Electrostatic high pressure | Electrostatic high voltage of 60-90kV. High voltage is easy to cause powder rebound and edge hemp point; low voltage and low powder rate. | |
Electrostatic current | Electrostatic current ranged from 10 to 20 μ A. High current is prone to discharge breakdown powder coating; low current and low powder rate. | ||
Flow rate pressure | Flow rate pressure 0.30-0.55MPa. The higher the flow rate pressure, the faster the deposition speed of the powder, which is conducive to quickly obtain the predetermined thickness of the coating, but too high will increase the amount of powder used and the wear speed of the spray gun. | ||
atomizing pressure | Nebulization pressure of 0.30~0.45MPa. Appropriate increase of atomization pressure can keep the thickness of the powder coating uniform, but too high will make the powder parts wear quickly to reduce the atomization pressure can improve the coverage ability of the powder, but too low is easy to make the powder parts blocked. |
Forming an electrostatic field
During electrostatic spraying, the workpiece is usually grounded as the positive electrode, and the spray gun or spray plate, spray cup, etc. are used as the negative electrode. The electrostatic field is generated by a high-voltage DC power supply of model JMDC-N80-1mA produced by Dalian Jeman Technology Co., Ltd. The paint particles are negatively charged due to corona discharge in the area near the end of the spray gun.
Paint is charged
After the paint is atomized by the nozzle, its particles are charged when they contact the electrode of the spray gun. In the gas ionization zone generated by corona discharge, the surface charge density of the paint particles is further increased.
Directed movement
Due to the principle of like repels like and opposites attract, negatively charged paint particles move toward the positive polarity of the workpiece surface under the action of the electrostatic field.
Deposition to form a coating
The charged paint particles are attracted and deposited on the surface of the workpiece to form a uniform coating. A thicker coating can be obtained in one coating, and the utilization rate of the paint is improved due to the reduction of paint mist dispersion.
It is worth noting that in order to achieve electrostatic spraying, the workpiece needs to be a conductor. For non-conductors such as plastics, wood products, etc., special treatment may be required to make them chargeable. In addition, the process parameters of electrostatic spraying such as voltage, current, flow rate pressure, etc. also need to be precisely controlled to ensure a good spraying effect.
