Evaluation of Degradation of Corrosion-Protective Paint Films by Electrochemical Impedance Method and Scanning Vibrating Electrode Technique

Abstract

The degradation of corrosion protective films of vinyl chloride resin, long oil alkyd resin containing lead cyanamide (Pb (CN) ₂), tar epoxy resin, and polyurethane resin was evaluated by electrochemical impedance spectroscopy (EIS) and scanning vibrating electrode technique (SVET). In this study, the film resistance (R_f) determined by EIS was closely correlated to the frequency at maximum phase angle (θ_max) measured with EIS. The breaking time (t_b1) of R_f-time curve also related to the breaking time (t_b2) of fθ_max-time curve. The relationship between the R_f by EIS and the current density (i) by SVET was also found clearly. The rapid measurements of fθ_maxby EIS and i by SVET were effective in the evaluation of the degradation of paint films.