The formation of pitting under dynamic DC interference: Corrosion product film defects or passive film induction

The cause of pitting under dynamic DC interference is unclear. This paper studies the mechanisms of pitting in simulated solutions under neutral and alkaline conditions using weight loss, electrochemical testing, and microscopic characterization. The results indicate that the metal mainly undergoes active corrosion in the neutral solution, and the formation of millimeter-scale pits is due to local defects in corrosion products. Metals in the alkaline solution undergo passive corrosion, resulting in micro-scale pits. Initially, stable pits form at damaged areas of the passivation film. Then, pits can grow rapidly under self-catalysis, with the growth rate surpassing other surface locations.