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Possibilité de détection à l’aide de la méthode des impédances électrochimiques

Detection of cathodic disbonding of organic coatings by the electrochemical impedance method

¹ Assistant
² Maître de conférences
³ Professeur, Ecole Centrale des Arts et Manufactures

Abstract

Electrochemical impedance measurements were archieved on coated steel plates. The organic was scratched and the plate was polarised under cathodic protection. The impedance measurements allowed us to detect the cathodic disbonding of the coating. In some cases, the “high frequency” (104-10 Hz) part of the Nyquist impedance plot was a straight line, with a slope equal to 1 ; this indicates the infiltration of a thin layer of electrolyte between the coating and the steel plate.

Howewer, a quantitative study of the cathodic disbonding mechanism (rate, extent) is not yet possible, from experimental impedance plots ; calibration experiments are required because the real structure and geometry of the thin layer are complicated and cannot be described by the other-simple assumptions of the existing models.