INTERACTIONS OF N,N'-DIMETHYLAMINOETHANOL WITH STEEL SURFACES IN ALKALINE AND CHLORINE-CONTAINING SOLUTIONS

Formulations based on dilute aqueous solutions of N,N'-dimethylethanol amine (DMEA) are used to protect reinforcement steel bars ('rebar') in concrete from corrosion. In a previous paper we discussed the usefuln ess of X-ray photoelectron spectroscopy (XPS) to detect DMEA adsorbed from solution and the application of secondary neutral mass spectromet ry (SNMS) to study migration of DMEA through a cement matrix. In this report we present XPS data of DMEA adsorbed on steel surfaces from alk aline and chlorine containing solutions of variable concentration rang e and discuss models for the interaction of DMEA with the oxidized ste el surface and the mechanism of corrosion inhibition of DMEA. DMEA is strongly bonded to the steel surface and displaces ionic species from the substrate/solution interface hence protecting the ironoxide surfac e from ionic attack. (C) 1997 Elsevier Science B.V.