Causes of bubble pinhole defects in local coating film after cathodic electrophoresis

    Analysis of the causes of bubble pinhole defects in the local coating film after cathodic electrophoresis:

    First, management impact

    Cathodic electrophoresis tank management requires 4kg of solvent per day in production and non-production. Due to National Day holiday, it is not added as required, resulting in solvent evaporation in the bath. However, except for the problematic part, the rear part No such phenomenon" After consultation with the paint manufacturer, 30 kg of solvent and 5 kg of acid were added to the bath, and the situation was not significantly improved. It is believed that the weather is too hot during the holiday, the amount of solvent volatilization is too large, the amount of addition is not enough, and 30 kg of solvent is added, which has not been solved. Defects should not be caused by insufficient solvent.

    Second, the cooling system

    After inquiring to the workshop staff, the cooling system of the electrophoresis tank failed during the holiday, causing the bath to rise to 32 ° C and rise to 35 ° C in individual time. We believe that due to the increase in bath temperature, air bubbles are generated in the bath, causing the horizontal plane of the workpiece to come into contact with the air in the bath when the tank is in the tank, resulting in the workpiece being separated from the bath, and there is no coating at the place where the air bubbles are present. Make the coating film incomplete and dull. The bath was allowed to stand for 2 hours for defoaming treatment, and then the product and the test piece were made, and the defects were solved. However, when it is normally produced, the defect appears again, but it is slightly lighter than before. "It can be seen that the temperature of the bath liquid is high in a short time to generate air bubbles, which is only one of the causes of defects.

    Third, equipment impact

    Check the pump associated with the electrophoresis tank! No leaks were found in the tube. However, the working pressure of the circulating pump of the bath failed to meet the process requirements, and the pipes related to the circulating pump of the bath were inspected one by one, and the metal filter was found to be clogged. Since the electrophoresis tank auxiliary circulation pump front end electrophoresis tank outlet filter is not installed, the metal filter and the pipeline are blocked, and some small air bubbles are generated into the human electrophoresis tank.

    The temporary solution is to stop the pump operation, stop the main circulation pump and the ultrafiltration circulation pump of the electrophoresis tank for two hours before production every day. After 3 days of treatment, the air bubbles are released; then the metal filter and the pipeline are cleaned. Ensure that the bath is unblocked and production returns to normal.

    Metal filters and pipe blockage are one of the major causes of defects.