How to improve the powder rate of dead corners by electrostatic spraying of electrostatic powder coatings

       November 19, 2021, How can electrostatic spraying of electrostatic powder coatings improve the powder rate of dead corners



  1. There are many factors affecting the powder loading rate of electrostatic powder coatings in the dead corners. There are many factors that affect the powder loading rate of electrostatic powder coatings. The two main theoretical factors are the charging effect of the powder and the shielding effect of the Faraday cage.



  2. Measures to solve the dead angle of electrostatic powder, improve the overall electrification of the formula, including the deployment of resin, fillers and additives, these three aspects are important factors that affect the powder rate of electrostatic powder in spraying.



  3. Materials, electrostatic powder coatings are mainly composed of epoxy, polyester resin and other macromolecular compounds. These compounds have high dielectric constants, so the electric field force is strong in the electric field. If only pure resin is used in the formula , the powder rate is good. However, due to the high price and cost, this method is generally not adopted. For the needs of their own market competition, powder manufacturers add fillers to reduce material costs and control the appropriate pigment-to-base ratio. Among them, fillers with fine particle size are added. Barium sulfate can improve the powder rate of dead corners.



  4. Charging auxiliaries: Most electrostatic powder coating manufacturers add charging auxiliaries to the powder formula to achieve the improvement of the powder on the dead corners of the electrostatic powder. Generally, metal powder, organic matter, and fine powder with large specific surface area are added.



  The electrostatic powder particles are pulverized and classified by suitable main and auxiliary mills, and the normal distribution of the obtained powder particle size is concentrated and the peak value is suitable. However, the particle size itself is very fine, and its own fluidity is very weak, which is not conducive to the electrification of the powder, and affects the powder rate of the dead corner of the powder. To improve the chargeability of powder particles, fumed silica or fine alumina powder can also be added during extrusion and pulverization. It can effectively improve the chargeability of the powder and increase the fluidity of the powder.



  5. The relationship between the particle size and the powder rate of the dead corners. Most of the materials of electrostatic powder coatings are materials with high insulating properties. Once the powder particles of a certain size are charged, it is difficult to disappear, and the resistivity of the powder is also large. Now powder factories generally control the median diameter D50 at 32 to 40 μm. The electrostatic powder in this particle size range has better powder loading rate in the electric field. Particles with larger particle size have higher electrification intensity, and are more likely to pass through the Faraday shielding effect area and deposit on the surface of the workpiece, and have a good powder rate in dead corners. Affected by unfavorable factors such as power, it is difficult to powder the dead corners. The electrostatic powder particle size that can better overcome the Faraday effect and promote the powder on the dead corner should be controlled within the range of 25-35 μm. The fine particle size (≤10μm) is controlled below 8%, the ultrafine powder is generally not charged, and is mainly affected by the air flow during the spraying process; the coarse particle size (≥70μm) is controlled below 3%, which can effectively avoid the edge of the groove It can solve the problem of thick coating and overcome the unfavorable factors such as the powder falling off the surface of the workpiece or the electrostatic powder with fine particle size being sucked away.