A comparison between electrochemical noise and electrochemical impedance measurements performed on a coal tar epoxy coated steel in 3% NaCl

The protective performance of epoxy coatings on mild steel immersed in 3.5% NaCl solutions was evaluated by means of electrochemical noise analysis and electrochemical impedance spectroscopy (EIS). Current and voltage noise were recorded and the standard deviations of the potential, current and noise resistance were calculated. Additionally, the spectral noise resistance (RSN) was obtained from the harmonic analysis of the noise data. Finally, EIS measurements were carried out and the data fitted with an equivalent circuit from which the polarization resistance was obtained. Resistance parameters obtained by both techniques were found to be in good agreement. A set of parameters obtained from electrochemical noise measurement is proposed to be used for the assessment of the performance of protective coatings.

► The protective performance of coatings was evaluated by means of electrochemical noise analysis and electrochemical impedance spectroscopy.
► Resistance parameters obtained by electrochemical noise are in good agreement with the ones obtained by electrochemical impedance.
► Electrochemical noise measurements provide a set of parameters which can be used for the assessment of the protective performance of the coating.
► An assessment based on various parameters obtained by electrochemical noise analysis permit a more sound assessment that the one that can be done with only one parameter.