Powder spraying application and technology

Powder spraying is a coating process in which the coating medium (i.e., powder) is charged and attached to a grounded workpiece. The powder attached to the workpiece mainly relies on the effect of electrostatic adsorption, and the workpiece attached to the powder also goes through the heating leveling and curing process in order to eventually form a complete film. Powder spraying process is a systematic project. Excellent spraying quality requires reliable before and after treatment, a high-quality powder coating system and powder to achieve.

Pre-spray treatment and curing

Before powder spraying, it is necessary to carry out the necessary pre-treatment of the workpiece to be coated, such as oil removal, rust removal, phosphating and water washing, etc., and grinding and other processes may be required when necessary. Only the workpiece with reliable pre-treatment can ensure uniform film thickness of the coating and firm adsorption. When the spraying is completed, it is necessary to send the spraying workpiece into the oven for baking within a certain time, so that the powder coating is heated to form a complete coating film according to different process requirements. Common curing methods include hot air circulation and thermal radiation baking.

The main component of powder coating system

A set of electrostatic powder spraying system is mainly composed of powder room, powder supply equipment, one or several sets of electrostatic spray guns and control devices, electrostatic generator and a set of powder recovery equipment.

♦ Powder feeding equipment

In the powder supply equipment, the powder is in a state of fluidization, which is achieved by the action of compressed air, and then the powder is carried by the flowing air through the siphon effect, forming a powder gas mixture, through the Venturi powder pump, powder pipe, and finally to the spray gun. The powder transported to the spray gun can be regulated, specifically, it is possible to adjust the parameters of the gas transmission and atomization gas, change the amount of powder and the atomization state of the powder, so as to achieve different film thickness to meet the needs of different products. The powder supply device must have sufficient capacity, even if the powder pipe of the gun is 20 meters long, it can provide sufficient pressure and flow.

♦ About static electricity

The high voltage and low current generated by the electrostatic generator make the electrode needle located in the front of the spray gun discharge in the air, and the powder is sprayed by the spray gun nozzle, bringing static electricity in the air, and reaching the surface of the grounded workpiece through the dual role of electrostatic adsorption and air transport. The spray gun can produce enough voltage to ensure the maximum coating effect, the maximum voltage can reach 100KV, when spraying the inner corner or deep cavity parts, the spray gun needs to effectively overcome the Faraday cage effect to ensure that each surface of the workpiece to be sprayed can achieve good coverage and uniform film thickness.

♦ Spray gun

The structural design of the spray gun must meet the charging requirements of the powder, and the functional design must meet the spraying requirements of various forms of spraying operations and various shapes of the workpiece.
The coating performance of powder spraying is concerned with the coating of spray painting process in terms of mechanical strength, adhesion, corrosion resistance, aging resistance, etc., and the cost is also under the spray painting with the same effect.