In real coating systems, the degradation of pigmented coating films was evaluated by the frequency at maximum phase angle (f[theta]max) obtained from electrochemical impedance measurement. The f[theta]max and film resistance (Rf) by electrochemical impedance measurement showed a linear relationship on a log-log plot. The degradation of coating films could be predicted by the determination of f[theta]max values. When the calculated values of f[theta]max and Rf were corrected by phenomenological coefficient ([beta]) in the range of 0 to 1, its linear relation was nearly consistent with that obtained in the measured values.