Components of electrophoretic coating production line

Components of electrophoretic coating production line

Electrophoretic coating requires the use of electrophoretic paint, also known as water-soluble coating. Electrophoretic paint and distilled water must be diluted in a certain proportion before use.

Electrophoretic coating generally involves four simultaneous processes:

1. Electrophoresis: Under the action of a direct current electric field, positively and negatively charged colloidal particles move in the negative and positive directions, also known as swimming.

2. Electrolysis: Oxidation reduction reactions occur on the electrodes, resulting in the formation of oxidation and reduction phenomena on the electrodes.

3. Electrodeposition: Due to electrophoresis, charged colloidal particles that move to the vicinity of the anode release electrons in the template surface and deposit in an insoluble state, resulting in the formation of a paint film.

4. Electroosmosis: The phenomenon in which the solid phase remains stationary while the liquid phase moves under the action of an electric field. Electroosmosis gradually discharges the moisture contained in the paint film to the outside, forming a dense paint film with almost no current passing through, extremely low moisture content, and high resistance.

5. Taking iron red epoxy electrophoretic paint as an example: This electrophoretic paint is composed of modified epoxy resin, butanol, ethanolamine, talc powder, and iron red. After mixing with distilled water, the electrophoretic paint is separated into positively charged cations and negatively charged anions under the action of a direct current electric field, and undergoes a series of complex physical, chemical, colloid, chemical, and electrochemical changes.

Methods and techniques for electric swimsuits

(1) The process flow of electrophoretic coating on general metal surfaces is: pre cleaning → online → degreasing → water washing → rust removal → water washing → neutralization → water washing → phosphating → water washing → passivation → electrophoretic coating → tank cleaning → ultrafiltration water washing → drying → offline.

(2) The substrate and pre-treatment of the coated material have a significant impact on the electrophoretic coating film. Castings are generally derusted by sandblasting or shot blasting, with cotton yarn used to remove floating dust on the surface of the workpiece, and 80 # to 120 # sandpaper used to remove residual steel balls and other debris on the surface. The steel surface is treated with degreasing and rust removal. When the surface requirements are too high, phosphating and passivation surface treatment are carried out. Black metal workpieces must undergo phosphating treatment before anodic electrophoresis, otherwise the corrosion resistance of the paint film will be poor. When phosphating, zinc salt phosphating film with a thickness of about 1-2 μ m is generally used, and the crystallization of the phosphating film is required to be fine and uniform.

(3) In the filtration system, a first stage filtration is generally used, and the filter is a mesh bag structure with a pore size of 25-75 μ m. The electrophoretic coating is transported by a vertical pump to a filter for filtration. Considering factors such as replacement cycle and paint film quality, a filter bag with a pore size of 50 μ m is preferred. It not only meets the quality requirements of the paint film, but also solves the problem of filter bag blockage.

(4) The circulation volume of the electrophoretic coating system directly affects the stability of the tank solution and the quality of the paint film. Increase the circulation volume, reduce the sedimentation and bubbles of the tank solution; But the aging of the tank solution accelerates, energy consumption increases, and the stability of the tank solution deteriorates. It is ideal to control the circulation frequency of the tank solution to 6-8 times/h, which not only ensures the quality of the paint film, but also ensures the stable operation of the tank solution.

(5) With the extension of production time, the impedance of the anode diaphragm will increase, and the effective working voltage will decrease. Therefore, in production, the working voltage of the power supply should be gradually increased according to the voltage loss situation to compensate for the voltage drop of the anode diaphragm.

(6) The ultrafiltration system controls the concentration of impurity ions introduced into the workpiece to ensure coating quality. During the operation of this system, it should be noted that the system should run continuously after operation, and intermittent operation is strictly prohibited to prevent the ultrafiltration membrane from drying up. The dried resin and pigment adhere to the ultrafiltration membrane and cannot be thoroughly cleaned, which will seriously affect the permeability and service life of the ultrafiltration membrane. The effluent rate of ultrafiltration membrane decreases with running time, and it should be cleaned once every 30-40 days to ensure the required ultrafiltration water for ultrafiltration immersion and flushing. (7) The electrophoretic coating method is suitable for large-scale assembly line production processes. The update cycle of electrophoresis bath solution should be within 3 months. Taking an electrophoresis production line with an annual output of 300000 steel rings as an example, scientific management of the tank solution is extremely important. Various parameters of the tank solution are regularly tested, and the tank solution is adjusted and replaced based on the test results. Generally, the parameters of the tank solution are measured at the following frequency: pH value, solid content, and conductivity of electrophoresis solution, ultrafiltration and ultrafiltration cleaning solution, cathode (anode) solution, circulating washing solution, and deionized cleaning solution once a day; Yanji ratio, organic solvent content, and laboratory small tank test are conducted twice a week.

(8) The management of paint film quality should regularly check the uniformity and thickness of the coating, and there should be no pinholes, sagging, orange peel, wrinkles or other phenomena on the appearance. The physical and chemical indicators such as adhesion and corrosion resistance of the coating should be checked regularly. The inspection cycle is based on the manufacturer's inspection standards, and generally each batch needs to be tested.

The application of electrophoretic coating and water-based paint marks a significant progress in the coating industry.

Electrophoretic coating has a fast construction speed, which can achieve mechanized and automated continuous operation, reduce labor intensity, uniform paint film, strong adhesion, and can obtain uniform, flat, and smooth paint film for areas that are difficult or poorly coated by general coating methods, such as rib plate welds and other areas mentioned earlier. The utilization rate of the coating is as high as 90% -95%, due to the electrophoretic coating being

Water, as a solvent, has the advantages of non flammability, non toxicity, and easy operation. The paint film dried after electrophoresis has excellent adhesion, and its rust resistance, corrosion resistance, weather resistance, and other properties are superior to ordinary paints and general construction methods.