The application of neutron reflectometry and atomic force microscopy in the study of corrosion inhibitor films

Abstract

In the search for new, superior and environmentally friendly corrosion inhibitor molecules, it is important to understand their mechanism of inhibition. Characterising the chemical and physical nature of the adsorbed inhibitor layer is a major part of understanding this mechanism. An accurate account of this character necessitates the use of surface analysis techniques that are capable of in-situ measurements. Ex-situ techniques are likely to cause changes either by oxidation of the metal and corrosion product film or rearrangement and loss of the inhibitor film during exposure to air and during the drying and analysis under vacuum. Neutron reflectometry in combination with atomic force microscopy provides the capability of in-situ surface analysis of thin interfacial layers. These complementary techniques make it possible to investigate the structure and orientation of molecules on a surface. which can ultimately assist in gaining an insight into the inhibitor mechanism. This paper will explore how these techniques can be used to determine the mechanism of corrosion inhibitors, with particular emphasis on surfactant molecules used to prevent carbon dioxide corrosion of steel during petroleum production. Results will be presented from experiments using the aforementioned in-situ surface analysis with generic corrosion inhibitor molecules cetyl pyridinium chloride (CPC), dodecyl pyridinium chloride (DPC), 1-hydroxyethyl-2-oleic imidazoline (OHEI) and cetyl dimethyl benzyl ammonium chloride (CDMBAC). These results will be further discussed with respect to the observed inhibition of carbon dioxide corrosion of carbon steel electrodes. © The Authors