Estimation of steel corrosion rate in reinforced concrete by means of equivalent circuit fittings of impedance spectra

Three equivalent circuit models were utilized to fit the alternating current (AC) impedance spectra obtained from the 5-year-old, 'lollipop-like' reinforced concrete samples. The RC parameters obtained from two of the equivalent circuit fittings were compared. Specifically, the differences in polarization resistance, Rp, and doublelayer capacitance, Cdl, were evaluated and the variation in the values of these elements found to be up to 70%. These two parameters were also determined from the fitting of the low-frequency portion of the corresponding impedance spectrum for the third equivalent circuit, and the differences were within 40%. The other RC parameters and their relationship with Rp, were also discussed. Finally, the corrosion rates of the 'lollipop-like' samples, determined from both the AC impedance and linear polarization methods, were compared and the differences in this study found to be about 100%.Trois (3) mod\ue8les de circuit \ue9quivalent ont \ue9t\ue9 employ\ue9s pour ajuster les spectres d?imp\ue9dance \ue0 courant alternatif (c.a.) qui ont \ue9t\ue9 obtenus \ue0 partir des \ue9chantillons de b\ue9ton arm\ue9 (BA) de forme ampoul\ue9e, \ue2g\ue9s de 5 ans. Les param\ue8tres de BA obtenus \ue0 partir de deux (2) des ajustements de circuit \ue9quivalent ont \ue9t\ue9 compar\ue9s. On a \ue9valu\ue9 sp\ue9cifiquement les diff\ue9rences dans la r\ue9sistance de polarisation Rp et la capacitance de la double couche Cdl, et la variation dans les valeurs de ces \ue9l\ue9ments s?est r\ue9v\ue9l\ue9e \ueatre de jusqu?\ue0 70 %. Ces deux param\ue8tres ont \ue9t\ue9 \ue9galement d\ue9termin\ue9s \ue0 partir de l?ajustement de la portion basses fr\ue9quences du spectre d?imp\ue9dance correspondant pour le troisi\ue8me circuit \ue9quivalent, et les diff\ue9rences \ue9taient en de\ue7\ue0 de 40 %. Les autres param\ue8tres de BA, ainsi que leur relation avec Rp ont \ue9t\ue9 \ue9galement examin\ue9s. Enfin, les vitesses de corrosion des \ue9chantillons de forme ampoul\ue9e, d\ue9termin\ue9es \ue0 partir de la m\ue9thode de polarisation lin\ue9aire et de la m\ue9thode de l?imp\ue9dance c.a., ont \ue9t\ue9 compar\ue9es, et les diff\ue9rences dans cette \ue9tude ont \ue9t\ue9 d?environ 100 %.Peer reviewed: YesNRC publication: Ye