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Electro-coating methods and techniques

Aluminium profile suppliers will introduce you the Electro-coating methods and techniques

(1) The processing of the electro-coating:
Pre-clean---On line---Oil removal---Washing---rust cleaning---Washing---Neutrailzation---Washing---Phosphating---Washing---Passivating---Electro-coating---Groove cleaning---Ultrafiltration water cleaning---Drying---Off line
(2) Substrates and pretreatment of the coating has a significant impact on the electrophoretic coating. Casting generally used sandblasting or shot blasting rust, with cotton yarn to remove dust on the surface of the workpiece, with 80 # ~ 120 # sandpaper to remove residual steel balls and other debris. Steel surface with degreasing and rust treatment, the surface requirements are too high, the phosphating and passivation surface treatment. Black metal parts in the anode electrophoresis before phosphating, or corrosion resistance of the paint film is poor. Phosphating treatment, the general choice of zinc salt phosphate coating, the thickness of about 1 ~ 2μm, require phosphate film thin and uniform crystallization.


(3) In the filtration system, the general use of a filter, filter for the net bag structure, pore size of 25 ~ 75μm. Electrophoretic coating is transported to the filter by vertical pumps for filtration. From a comprehensive replacement cycle and paint quality considerations, the best filter bag pore size of 50μm, it not only to meet the quality requirements of the paint film, but also to solve the clogging of the filter bag.
(4) Electrophoretic coating circulating system circulation size, directly impact on the stability of the bath and the quality of the film. Increasing the amount of circulation, bath precipitation and bubble reduction; but accelerated aging tank, energy consumption increases, the stability of the bath worse. The number of cycles to control the bath 6 to 8 times / h is ideal, not only to ensure the quality of the paint film, but also to ensure the stable operation of bath.
(5) With the extension of production time, the impedance of the anode diaphragm will increase, the effective operating voltage drop. Therefore, the production should be based on voltage loss, and gradually increase the power supply voltage to compensate for the anode diaphragm voltage drop.

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(6) Ultrafiltration system to control the concentration of impurity ions into the workpiece to ensure coating quality. In the operation of this system should be noted that the system should run continuously after operation, it is strictly prohibited intermittent operation, in case the ultrafiltration membrane dry. After drying the resin and paint attached to the ultrafiltration membrane, can not be thoroughly cleaned, will seriously affect the ultrafiltration membrane water permeability and service life. UF membrane effluent rate decreased with the running time and continuous work for 30 to 40 days should be cleaned once, in order to ensure ultrafiltration and rinse required ultrafiltration water.
(7) Electrophoresis coating method for a large number of assembly line production process. Electrophoresis bath liquid renewal period should be within 3 months. Taking an electrophoresis production line with an annual output of 300,000 steel coils as an example, the scientific management of the bath is very important. Various parameters of the bath are regularly tested, and the bath is adjusted and replaced according to the test results. Generally, the parameters of the bath liquid are measured according to the following frequencies: electrophoresis liquid, ultrafiltrate and ultrafiltrate washing liquid, pH value of the anion (positive) polar liquid, circulating washing liquid and deionized washing liquid, solid content and electric conductivity once a day; Base ratio, organic solvent content, laboratory test small tank twice a week.


(8) The quality of the paint film should always check the uniformity and film thickness, the appearance should not have pinholes, sagging, orange peel, wrinkles and other phenomena, regularly check the coating adhesion, corrosion resistance and other physical and chemical index. Inspection cycle by the manufacturer's test standards, the general need to test each batch. Thickness 5-30μm.

 

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