Monitoring of Localized Corrosion with Electrochemical Impedance Spectroscopy (EIS)

Abstract

Abstract Experimental evidence collected by the authors shows that the growth of pits on Al alloys and Al-based metal matrix composites can be monitored by EIS. Characteristic changes occur in the impedance spectra when pits have exceeded a certain minimum depth. The phase angle is especially sensitive to the initiation of pits. A model for the impedance of pitted Al surfaces has been developed. The procedure for fitting experimental EIS-data to this model has been illustrated. The growth of pits and its time dependence can be followed based on the values of the polarization resistance R°pit of a growing pit. Pit growth laws for Al 7075-T6 and Al 6061 exposed to 0.5 N NaCl have been derived.