SYMPOSIA PAPER Published: 01 January 1993
STP18061S

Specific Aspects of Impedance Measurements in Low Conductivity Media

Source

Impedance measurements in the high frequency range, namely f > 1 kHz, often exhibit one or several loops irrelevant to the electrode process. For low conductivity media, encountered in corrosion studies such as in natural waters or in organic solvents, these relaxations also appear at a lower frequency range. This may lead to a possible misinterpretation of data by mistaking them for faradaic relaxation phenomena. The influences of the solution resistivity, the position of the Luggin capillary tip, and the nature of reference electrode were extensively studied. The corrosion of austenitic stainless steel in acetic acid was used as a model system. The conductivity of acid was changed by varying the water content. The reference electrode was either Ag/AgCl or the tip of a platinum wire embedded in a glass capillary. The results allowed us to propose an equivalent electrical circuit. The circuit is described as a capacity divider bridge (due to the stray capacitances between reference/working and reference/counter electrodes) and by the electrolyte resistance inside the capillary tip. The numerical simulations fit the experimental data well.

Author Information

Chechirlian, S
Centre de Recherche, Rhône Poulenc, Décines, France
Keddam, M
CNRS, Physique des Liquides et Électrochimie, Laboratorie de l'Université P&M Curie, Paris, France
Takenouti, H
CNRS, Physique des Liquides et Électrochimie, Laboratorie de l'Université P&M Curie, Paris, France
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Details
Developed by Committee: G01
Pages: 23–36
DOI: 10.1520/STP18061S
ISBN-EB: 978-0-8031-5240-3
ISBN-13: 978-0-8031-1861-4