SEDL / STP / STP1188-EB / STP18076S

Detection and Monitoring of Localized Corrosion by EIS

Mansfeld, F
University of Southern California, Los Angeles, CA

Wang, Y
University of Southern California, Los Angeles, CA

Lin, SH
University of Southern California, Los Angeles, CA

Xiao, H
University of Southern California, Los Angeles, CA

Shih, H
University of Southern California, Los Angeles, CA

Pages: 16    Published: Jan 1993

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Abstract

Experimental evidence collected by the authors shows that the growth of pits on aluminum 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 aluminum 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, Al 7075-T73, and Al 6061 exposed to 0.5 N NaCl have been derived. Pit growth rates are inversely proportional to the exposure time.