Monitoring the corrosion behaviour of chromate-passivated aluminium alloy 2014 A-T6 by electrochemical impedance spectroscopy during salt fog exposure

Electrochemical impedance spectroscopy (EIS) of unpassivated and chromate-p assivated Al 2014 A-T6 was carried out at intervals during the course of ne utral salt spray corrosion tests. At given time intervals, the samples were removed from the salt fog cabinet in order to perform EIS in 3.5% NaCl at an open circuit potential with a 10 mV a.c. amplitude. For unpassivated Al 2014 A-T6, impedance results were found to mirror well the observations mad e during salt fog exposure. However, for chromate-passivated Al 2104 A-T6, it was found that the onset of coating deterioration occurred long before t he development of white corrosion product was observed on these surfaces. ( C) 1999 Elsevier Science S.A. All rights reserved.