Electrophoretic coating is a highly popular spraying method and one of the most effective techniques for coating metal workpieces. It is widely applied in industries such as automotive, construction materials, hardware, and home appliances. When using electrophoretic coating production lines, strict requirements are placed on the uniformity and thickness of the paint film—it must neither be too thick nor too thin. However, due to objective or subjective factors, failure to monitor the process in real time often results in excessively thin electrophoretic films.
Below, we outline the common causes of thin electrophoretic films and their corresponding solutions:
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Reduced Solids Content in Bath Solution: Increase solids content to within process specifications.
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Bath Temperature Below Process Range Solution: Regularly clean the heat exchanger; check the heating system and temperature sensors for faults. Maintain bath temperature within the process range.
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Low Electrophoretic Voltage Solution: Increase electrophoretic voltage.
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Insufficient Coating Time Solution: Extend coating time.
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Low Bath pH Value Solution: Adjust pH to the appropriate range.
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Low Bath Conductivity Solution: Reduce ultrafiltrate discharge.
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Poor or Damaged Electrode Contact Solution: Inspect electrode plates for corrosion or scaling; clean or replace electrodes regularly.
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Poor Electrical Contact on Workpiece; Paint Buildup on Hanger Contact Points Solution: Verify workpiece electrical continuity; remove paint from hanger contact points.
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Lightweight Workpiece Suspended in Circulation Flow, Resulting in Poor Conductivity Solution: Secure workpiece contact with the hanger.
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Poor Power Supply Contact (Low Current) Solution: Inspect power supply and terminal connections.
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Improper Cathode-to-Anode Plate Ratio Solution: Maintain cathode-to-anode area ratio generally between 4:1 and 2:1.
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Severe Corrosion of Anode Plates or Tubes Solution: Inspect anode plates/tubes and replace corroded parts.
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Low Organic Solvent Content in Bath Solution: Add solvent to bring it within process range.
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Aged Bath Liquid; Excessively High Wet Film Resistance and Low Conductivity Solution: Replenish with fresh material and accelerate bath turnover.
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Low Voltage and Excessively Short Coating Time Solution: Increase coating voltage and extend time (typically 2–3 minutes based on film thickness requirements).
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Low Anode Liquid Conductivity Solution: Increase anode liquid conductivity.
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Excessive UF Rinse Time After Electrophoresis Causing Redissolution Solution: Shorten UF rinse or post-rinse duration; discharge some ultrafiltrate and replenish with deionized water to prevent redissolution.
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Low Bath pH and High MEQ Value Solution: Discharge ultrafiltrate and replenish with fresh material.
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Excessively Thick Phosphating Film Causing High Resistance Solution: Adjust phosphating process to control film thickness.