09221 Inhibition Mechanism in Concrete by Organic Substances: An Experimental and Theoretical Study

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Product Number: 51300-09221-SG

ISBN: 09221 2009 CP

Author: Elmer Perez, Luciano Lazzari, Fabio Ganazzoli, Marco Ormellese and Giuseppina Raffaini

Publication Date: 2009

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Corrosion inhibitors are one of the preventative techniques used to prevent chloride-induced corrosion in reinforced concrete structures. Several commercial inhibitors are available on the market, but their efficiency as well as their inhibitive mechanism are not well understood. In this paper the inhibiting behaviour of five organic substances in delaying chloride-induced corrosion was evaluated in alkaline solution using electrochemical impedance spectroscopy and potentiodynamic tests. The studied substances were sodium tartrate, sodium benzoate, sodium glutamate, dimethylethanolamine (DMEA) and triethylenetetramine (TETA). The best results were obtained with tartrate and benzoate. To establish the interaction between inhibitors and passive film, theoretical calculations based on molecular mechanics and molecular dynamics were used, as well as Langmuir-Freundlich and Temkin adsorption isotherms were established from the experimental results. The theoretical results showed the presence of a favourable interaction energy with the surface of the adsorbed molecules, with repulsive intermolecular interactions, mainly among the anions. The adsorption isotherms confirmed both the presence of a strong physisorption between the inhibitors and the substrate, and of repulsive interactions between the molecules of inhibitors, leading to the formation of a non-homogenous monolayer, i.e. a layer of inhibitor molecules scattered across the surface.

Keywords: organic inhibitors; mechanism; EIS; molecular mechanics; molecular dynamics; adsorption isotherms; chloride-induced corrosion.