Detection and Characterization of Dimethylethanolamine-based Corrosion Inhibitors at Steel Surfaces. I. The Use ofXPS and ToF-SIMS

Abstract

Formulations based on dilute aqueous solutions of N,N-dimethylethanolamine (DMEA) are used to protect reinforcement steel bars ('rebar') in concrete from corrosion. In a series of papers we will discuss the mechanism of corrosion inhibition and migration of DMEA through a cement matrix. Here we investigate the usefulness of XPS and SIMS in detecting the presence of DMEA at Au and steel surfaces, and in providing quantitative and chemical state information after various treatment schemes. We conclude that XPS can provide semi-quantitative information down to a coverage level which depends on the amount of other contaminant species present. Some useful information on chemical states is provided from exact core-level binding energies. Secondary ion mass spectrometry in the high mass resolution static mode, using time-of-flight, provides direct evidence for the presence of specific molecular or fragment components of DMEA, which XPS cannot identify. SIMS can, therefore, be used as a 'tracer' for the presence of DMEA, even in the presence of strong contamination. Both methods reveal differences in the surface chemistry after differing surface treatments.