Electrochemical Characteristics and Equivalent Circuit Representation of Mortar-Coating-Steel Systems by EIS

Abstract

This paper summarizes an experimental study on the electrochemical characteristics of various mortarcoating-steel systems and on the equivalent electrical circuit modeling for their representative behaviors. Mortar cylinders with uncoated, enamel-coated, and fusion bonded epoxy (FBE)-coated steel bars were investigated in 3.5 wt.% NaCl solution up to 244 days using electrochemical impedance spectroscopy (EIS). The microstructure of a mortar-coating-steel system was examined using scanning electron microscopy (SEM), and the effects of water cement ratio and exposure condition were considered. SEM images showed a thin porous mill scale on the surface of uncoated steel bars, a 150 μm thick coating with air bubbles of enamel-coated bars, and a 300 μm thick coating with air bubbles distributed near the FBE-coated steel bars. EIS results indicated that the frequency ranges of mortar/coating matrix, passive film, and solution-steel interface can be completely separated for specimens with uncoated steel bars, and but not for specimens with enamel and FBE-coated steel bars. Moreover, the mortar-coating-steel systems can be modeled by an electrical circuit that consists of a series of components representing different material layers. The effect of water cement ratio on the evolution of impedance spectra was less significant than the effect of exposure conditions.

Meeting Name

Corrosion: Collaborate. Educate. Innovate. Mitigate. (2014: Mar. 9-13, San Antonio, TX)

Department(s)

Civil, Architectural and Environmental Engineering

Second Department

Materials Science and Engineering

Keywords and Phrases

Scanning electron microscopy, Electrochemical characteristics; Equivalent electrical circuits; Steel-concrete interface; Electrochemical impedance spectroscopy

International Standard Serial Number (ISSN)

0361-4409

Document Type

Article - Conference proceedings

Document Version

Citation

File Type

text

Language(s)

English

Rights

© 2014 National Association of Corrosion Engineers (NACE) International, All rights reserved.

Publication Date

01 Mar 2014

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