An X-ray spectromicroscopy study of the corrosion of polymer coated steel

Fri., Sep. 10, 2021 3:30 p.m. - Fri., Sep. 10, 2021 4:30 p.m.

Location: Zoom

Abstract: Corrosion of concrete embedded steel reinforcing bar (rebar) resulting in damage to the surrounding concrete is a major concern. This concern is particularly pronounced for the potash (KCl) industry where high chloride environments exacerbate corrosion. Polymer coated rebar is one of the corrosion mitigation strategies that can be implemented, however methods to nondistructivly study the corrosion of polymer coated rebar are limited. These methods normally either provide information on corrosion rate but with no spatial sensitivity or require destruction (i.e. removal of the polymer) of the sample to study corrosion underneath. This talk will cover progress that has been made over the past five years at the University of Saskatchewan to develop synchrotron-based methodologies to studying this polymer rebar interface while gaining insight into the failure mechanism of polymer coatings.

The basis of much of this research has been a combination of X-ray microprobe mapping using multiple excitation energies and Fe K-edge micro X-ray absorption near edge spectroscopy (µ-XANES). An excitation energy of 7115 eV is used for X-ray microprobe mapping because of the difference in absorption cross-sections between Fe metal and oxidized Fe in corrosion products. The difference in absorption cross-section at 7115 eV results in higher fluorescent photon intensities being observed in regions of Fe Kα1 X-ray microprobe maps that contain higher concentrations of Fe metal whereas lower fluorescent photon intensities are observed in regions that contain higher concentrations of corrosion products. This is because the higher absorption of Fe metal at 7115 eV causes higher fluorescence emission when compared to the lower absorption and subsequent lower fluorescence emission from corrosion products. Fe K-edge µ-XANES can then be performed to determine the Fe speciation at selected locations of interest by performing linear combination fitting (LCF) using Fe K-edge standards.

This talk will also briefly cover some of the research Dr. Arthur Situm is performing at the University of Western Ontario as part of this postdoctoral fellowship related to the corrosion of nuclear materials. Specifically, this research is focused on the atmospheric corrosion of copper in conditions relevant to the environment within a planned deep geological repository (DGR) for Canada’s used nuclear fuel.

Speaker: Dr. Arthur Situm, University of Western Ontario