Cathode electrophoresis after partial coating. Bleb pinhole defects

       Source: China coating network

After the cathodic electrophoretic partial coating. Bleb pinhole defects cause analysis:

A, management effect

Cathodic electrodeposition bath management requirements in production and not production every day under the condition of adding 4 kg of solvent, due to the National Day holiday, did not add, as required, results in a solvent evaporation in the bath, "but, in addition to the defective parts, followed by parts of no the phenomenon" of consulting coating manufacturer technicians, to solvent bath, adding 30 kg and 5 kg of acid, no obvious improvement. Think the weather is too hot during the holiday, solvent volatilization amount is too large, add enough quantity, and add 30 kg solvent, remains unresolved. Defects should not caused by a lack of solvent.

Second, the cooling system

After asked the workshop personnel, in the electrophoresis tank during the holiday is a fault in the cooling system, lead to bath to 32 ℃, individual time up to 35 ℃. We think because of bath temperature, results in a produced air bubbles in the bath, bath of workpiece surface parts in one slot with exposed in the air, result in artifacts from the bath, free of air bubbles place without coating, the coating is not complete, matt. The slot liquid static defoaming 2 h, and then do products and specimens, defect is resolved. However, when the normal production, the defects appeared again, just to slightly than before "visible, bath temperature on the high side in a short time to produce the air bubble is one of the causes of the defects.

3, equipment

Check the electrophoresis tank related pump! Pipe leakage phenomenon has not been found. But the slot liquid circulating pump working pressure can not meet the technological requirements, circulating pump of bath and given relevant piping, found that the metal filter blocking phenomenon. Because the electrophoresis tank auxiliary circulation pump front electrophoresis tank outlet screen pack not installed, metal filter and blockage, produced a number of small air bubbles into the electrophoresis tank.

Temporary solution is to stop the pump running, a day before production stop electrophoresis groove of the main circulation pump and the ultrafiltration circulation pump for two hours, after three days of treatment, the air bubble is released; And then to metal pipes and filters to clean up, ensure smooth slot liquid production back to normal.

Metal filters and the pipeline jam is one of the important cause of the defects.

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