Treatment Method of Rectangular Tube Spraying

The use of compressed air and spray gun to atomize the paint to construct the rectangular tube is called the spray method, which is characterized by the uniform thickness of the coating film obtained, the appearance is smooth, and the production efficiency is high. The following three processing methods for rectangular pipe spraying are introduced:

1. Electrostatic spraying

During electrostatic spraying, an electrostatic generator is used to generate a high-voltage electric field. The spray gun and the object to be coated are connected to both ends of the high-voltage electric field. The paint sprayed from the spray gun is atomized in the high-voltage electric field and deposited on the surface of the rectangular tube under the action of the electrostatic force. , forming a uniform coating film. When spraying, due to the good atomization effect of the coating, the loss is very small, the utilization rate of the coating can reach 80%-90%, and the quality of the coating film is good, which can realize continuous production. The technical requirements of electrostatic spraying are relatively high, and there are certain process requirements for paint, electrostatic spraying equipment, spraying voltage, distance between the coated object and the spray gun, and the flow and setting of the spray gun.

When spraying, the rectangular tube is generally grounded as the anode, and the nozzle is negative high voltage. When the electric field strength is high enough, the air near the muzzle will generate corona discharge, which will ionize the air. When the paint particles pass through, they are charged to become charged particles, and when they pass through the corona discharge zone, they are further combined with ionized air and charged again. Under the action of high-voltage electrostatic field, it is brought to the surface of the rectangular tube with positive polarity, thereby depositing to form a coating film.

2. Air spray

Using the negative pressure generated by the compressed air in the spray gun nozzle, the paint in the paint container is sprayed from the paint nozzle, and immediately enters the high-speed compressed air flow, so that the paint liquid rapidly diffuses in a gas phase, and is dispersed into mist-like particles and shoots towards the object to be coated. , evenly coated on the surface. This method requires that the viscosity of the paint is relatively small, and diluents are often added to the paint. When the rectangular tube is used for air spraying, the spraying distance of the spray gun, the operation mode of the spray gun, the pattern overlap of the spray and the viscosity of the paint should be mastered.

The characteristics of this spraying method are:

1) The quality of the coating film is good, uniform and the adhesion to the coated surface is improved;

2) The paint loss is large and the utilization rate is low, which is not conducive to environmental protection;

3) Strong applicability;

4) High coating efficiency.

3. High pressure airless spraying

The high-pressure pump is driven by compressed air, and the paint is sucked in and pressurized, and sprayed through the hose and spray gun. When the high-pressure paint leaves the nozzle, it is quickly atomized into extremely fine particles and sprayed onto the surface of the rectangular tube to form a uniform coating film. In airless spraying, the paint itself is pumped to high pressure by a high-pressure pump and is not mixed with compressed air, unlike the above-mentioned air spraying when compressed air atomizes paint. At the same time, the coating is sprayed to the surface of the coated object under the pressure of 10-25MPa, which greatly improves the penetration ability of the coating, the adhesion of the coating film is good, and the coating film has a smooth and dense appearance. The main equipment for airless spraying of rectangular pipes includes power sources such as compressed air or electric pressure sources, high-pressure pumps, filters, paint pipes, paint containers and spray guns. Airless spraying is divided into cold spraying and thermal spraying. Thermal spray can be used to spray high solids, high viscosity coatings.