Sendtime：2019-12-14 source：Makersoon Powder Coatings
Powder Coatings has the characteristics of high production efficiency, excellent film performance, good ecological environmental protection and outstanding economy. In production, equipment manufacturers improve the dusting rate on dead corners through the improvement of electrostatic equipment spray guns and equipment technical changes. There are many factors that affect the powder rate at the dead corner of powder coatings, which can be divided into external factors and internal factors. The external factors include the size and shape of the corners of the coated workpiece, the customer's dusting system, the dusting construction personnel, etc., and the operational factors in the powder formulation adjustment and spraying process are internal factors.
Low-temperature Curing Powder Coatings
As a Powder Coatings Supplier, I would like to share with you two main theoretical factors that influence the powder rate at the dead corner of powder coatings, namely the charging effect of the powder and the Faraday cage shielding effect.
I. Powder charging effect:
The electrical effect of the powder determines the charge carried by the powder itself and affects the deposition rate of the powder particles on the workpiece on the grounded surface. The sprayed powder is subjected to an electric field force. After the particles reach the surface of the workpiece, the charged particles slowly dissipate the charge, and a secondary electric field is gradually formed on the surface. The powder is deposited on the surface of the workpiece under the action of the electric field. When the powder reaches a certain thickness, the electric field gradually weakens and the powder is powder The rate becomes worse. Therefore, the thickness of the coating on the surface of the workpiece is affected by the average particle charge and the thickness of the coating film. It can be inferred that the charging effect of the powder affects the important factors of the powder on the dead corner.
Faraday cage effect:
The powder is sprayed on the surface of the workpiece. The strong electric field released by the ordinary corona spray gun has a very prominent advantage. The powder rate is good on the entire surface, but when the surface of the workpiece has deep pits or grooves, it often encounters the Faraday cage effect, such as Figure 1.The sprayed powder particles will be concentrated at the lower resistance of the power line (that is, the edges of these depressions). Because the field strength at the edges increases, the powder particles will move directly to the edges. The powder deposition in these places is obvious. It is difficult to reach the groove, which is what we usually call the Faraday cage effect.
Theoretically, when a thick powder layer is applied at the edge, other powder particles can no longer be deposited there, and the only place to go is to enter the bottom of the deep depression. The actual situation is not the case. Practical examples show that the powder cannot reach the bottom of the groove of the workpiece. First, because the particles are strongly pushed to the edge of the Faraday cage by the electric field, only a few particles have the opportunity to enter the recessed part. Second, the free particles generated by the corona discharge will move along the power line to the edge of the workpiece, causing the existing coating to be quickly saturated with excess charge, so that the reverse ionization is very strong, forming a groove vacuum, and the interior is not charged. It is impossible to deposit powder particles, so it is difficult to powder on the dead end.
When discussing the rate of powder on the dead end of the powder, there are multiple factors acting together, and the internal and external factors must be distinguished. External factors include the size and shape of the corner of the coated workpiece, customer dusting system, dusting construction personnel, etc. These factors also affect the powder rate at the dead corner, which is a factor that cannot be ignored.
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