Controlling electrode fouling in pulsed electric field (PEF)-based disinfection of spoiled E-coating paints

Abstract The present study investigated the feasibility of applying pulsed electric field (PEF) treatment in anodic electrodeposition (AED) paints without inducing undesired paint deposition on electrode surfaces. PEF treatment is a promising non-thermal technique for microbial inactivation and control in E-coating lines. However, paint deposition on treatment electrodes can cause operational limitations. This study investigates paint stability, coating performance, and electrodeposition mechanisms during PEF treatment of industrial AED emulsions. Using both unipolar and bipolar square-wave pulses at varying durations and charge symmetry, deposition behavior and paint quality were evaluated under continuous flow for PEF treatments known to induce at least a 99% bacterial inactivation on bacteria isolated from E-coating lines. Intensive and repeated PEF treatment of AED paint did not impair the quality of the subsequent coating and did not change the properties of the paint. Paint quality remained unaffected across all trials. Regarding the coagulation and paint deposition on the PEF treatment electrodes, results show that unipolar pulses induce paint coagulation at the anode, even at short durations (when pulses are in the range of the double layer threshold time ≥ 1 µs). In contrast, bipolar pulses with nominal pulse durations ≤ 1.5 µs (0.75 + 0.75 µs) prevented electrode fouling and allowed uninterrupted treatment for over 10 h, without electrode fouling. Furthermore, the application of charge-symmetrical bipolar (CS-bipolar) pulses eliminated deposition entirely, even at nominal durations up to 2.9 µs (1.48 + 1.41 µs). Findings demonstrate that pulse polarity, charge balance, and field symmetry are critical for deposition-free PEF operation in AED systems. These insights provide a technical foundation for scaling PEF in industrial paint processing.