Monitoring the degradation of a high solids epoxy coating by means of EIS and EN

This paper reports a study of the degradation processes suffered by steel samples painted with a high solid content epoxy coating. Because this coating shows a high resistance when exposed to NaCl solutions, HCl solutions were employed to accelerate the corrosion processes. Macroscopic images were used to observe the coating degradation. Then electrochemical techniques, electrochemical impedance spectroscopy (EIS) and electrochemical noise (EN) were employed to monitor the corrosion behaviour of the system studied. A close correlation was found between EIS and EN data. Several parameters were estimated using these techniques: Rpo, Rct, Cc, Cdl and Z0.1 Hz using EIS, and Rn using EN. In addition, a new parameter estimated by means of EN was employed, Z0.1 Hz(EN). The evolution of all these parameters with time enabled the effective monitoring of the degradation stage of the coating.