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Relating the corrosion inhibitor efficacy to adsorbed film structure
Conference paper

Relating the corrosion inhibitor efficacy to adsorbed film structure

S Bosenberg, D John, T Becker, S Bailey, Roland De Marco and B Kinsella
Proceedings of the 2008 European Corrosion Congress, p.328
European Corrosion Congress (EUROCORR): Managing Corrosion for Sustainability, 2008 (Edinburgh, United Kingdom, 07-Sep-2008–11-Sep-2008)
Institute of Materials Engineering Australasia Pty. Ltd.
2008
url
http://www.iom3.org/events/eurocorr-2008-european-corrosion-congress-managing-corrosion-sustainabilityView
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Abstract

corrosion sustainability
While carbon dioxide corrosion inhibitors have been used for many years for the protection of oil and gas pipelines, their true mechanism of action remains largely unknown. Traditionally, the methods used for determining an inhibitors' efficiency have involved dosing the inhibitor without consideration for the properties of the active component. Furthermore, the techniques that are employed to physically observe the inhibitor film have been ex-situ and/or with model surfaces, thereby only offering an approximation as to the surface structure formed by the adsorbed inhibitor. The active component of a commercial inhibitor formulation contains one or more surfactant molecules. A unique property of surfactants is their ability to form micelles, or aggregates, of surfactant molecules above the critical micelle concentration (cmc). It has recently been demonstrated that the efficiency of the inhibitor does not improve significantly when dosed above the cmc in a hydrochloric acid media, and it is postulated that this trend holds true when applied to carbon dioxide corrosion conditions. In solution, various different shaped micelles have been identified above the cmc. Using a technique called atomic force microscopy (AFM), it has recently been shown that the same basic micellar shapes that form in the bulk solution translate to the surface. The advantage of AFM is its ability to image in-situ and on real surfaces, such as steel, at a molecular level giving a closer representation of the structure at the solid liquid interface. This paper demonstrates the shapes of micelles that are formed on steel surfaces in pure water and synthetic brine, and correlates these shapes to the inhibitor efficacy. This is an important development for examining the adsorption of corrosion inhibitors on steel, as it gives the physical structure of the assembled molecules is revealed at the molecular level.

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