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

摘要

Electrochemical impedance spectroscopy (EIS) of unpassivated and chromate-passivated Al 2014 A-T6 was carried out at intervals during the course of neutral 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 made during salt fog exposure. However, forchromate-passivated Al 2104 A-T6, it was found that the onset of coating deterioration occurred long before the development of white corrosion product was observed on these surfaces.