Defects of the most popular cathodic electrophoret

2022-08-01
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Disadvantages of cathodic electrophoretic paint film and its prevention and cure

particles (pimples): there are rough (or visible) hard particles on the surface of the dried electrophoretic paint film, which are called particles

cause:

1 tank liquid is poorly filtered, and there are deposits, condensates or other foreign matters in the electrophoresis tank liquid

2 after electrophoresis, the washing solution is dirty or the paint concentration in the washing water is too high

3 the drying oven is dirty

4 the water after phosphating is not clean, and the coating entering the electrophoresis tank is dirty

5 the coating environment is dirty, and the wet film after phosphating and electrophoresis is polluted when drying

6 the alkalinity of the subsequent rinsing water is too high, which makes the paint solution that cannot be rinsed off have poor solubility in the water

7 the paint flow on the surface of the bath liquid is poor, and there are too many bubbles on the surface of the bath liquid

8 pretreatment did not remove the oxide particles on the metal surface

9 the paint film is less than a certain thickness

10 the concentration of impurity ions in the paint bath is high, or alkaline impurities are brought into the bath, making the electrophoresis resin separate from the water

prevention and treatment methods:

1 try to avoid dust into the paint tank and strengthen the filtration of electrophoresis tank solution. During the foaming process, all circulating paints can also be mechanically stirred instead of manually stirred. The liquid shall all pass through the filtering device. During the design of the paint tank, try to avoid "dead corners" to avoid the sedimentation of pigments and fillers

2 frequently change the cleaning fluid in the back channel. It is better to filter the cleaning fluid and make an overflow port to reduce the foam on the surface of the cleaning fluid

3 clean the drying room and air filter regularly, check the balance system and air leakage, and do not slack off

4 strengthen the washing after phosphating, and clean the phosphating residue floating on the workpiece surface. Check whether the filter of deionized water circulating washing tank is blocked according to experts to prevent secondary pollution of the coated surface

5 the painting environment shall be kept clean. The phosphating and electrophoresis can also be dialed to the manufacturer's tank and drained after electrophoresis (before entering the drying room). A partition wall shall be set to check and eliminate the dust source in the surrounding air

6 the pH of the rear cleaning water shall be controlled at neutral

7 increase the surface velocity of the bath liquid

8 remove the oxide particles on the workpiece surface by grinding

9 the film thickness shall be controlled within the required range

10 avoid bringing alkaline impurities and other impurity ions into the electrophoresis tank. Discharge ultrafiltration frequently to remove impurity ions in the tank

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