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Accession Number:
ADA331162
Title:
The Use of Electrochemical Impedance Spectroscopy (ElS) and Electrochemical Noise Analysis (ENA) for Monitoring of Biocorrosion, Tri-Service Committee on Corrosion Proceedings.
Descriptive Note:
Corporate Author:
UNIVERSITY OF SOUTHERN CALIFORNIA LOS ANGELES DEPT OF MATERIALS SCIENCE AND ENGINEERING
Report Date:
1994-06-01
Pagination or Media Count:
24.0
Abstract:
The use of electrochemical impedance spectroscopy EIS and electrochemical noise analysis ENA for non-destructive evaluation of corrosion processes is illustrated for three model systems. EIS can be used to detect and monitor localized corrosion of Al alloys and determine pit growth laws which can be used for lifetime prediction purposes. Electrochemical potential and current noise data can be analyzed in the time and the frequency domain. A comparison of noise data obtained for Pt and an Al 2009SiC metal matrix composite MMC exposed to 0.5 N NaCI has shown that the use of potential noise data alone can lead to misleading results concerning corrosion kinetics and mechanisms. The electrochemical noise data have been evaluated using power spectral density PSD plots in an attempt to obtain mechanistic information. The system FeNaCI has been used to determine the relationship between the polarization resistance Rp obtained from EIS data and the noise resistance Rn determined by statistical analysis of potential and current noise data. Potential and current noise can be recorded simultaneously allowing construction of noise spectra from which the spectral noise resistance Rosn can be obtained as the limit for zero frequency. Good agreement between Rp Rn and Rosn has been observed for iron exposed to NaCI solutions of different corrosivity. For polymer coated steel exposed to 0.5 NaCI for five months analysis of EIS data allows to draw conclusions concerning the degree of disbonding of the coating and the decrease of the coating resistivity with exposure time. Rn and Rosn obtained from electrochemical noise data for an alkyd coating on cold rolled steel agree with each other and show the same time dependence as Rp and the pore resistance Rpo determined from EIS data, but are significantly lower than Rp and Rpo.
Distribution Statement:
APPROVED FOR PUBLIC RELEASE
