Characterization of the surface film formed from carbon dioxide corrosion on N80 steel

Abstract

X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM) and X-ray diffraction (XRD) were employed to systematically characterize the chemical composition and the microstructure of the surface film on N80 oil tube steel exposed to carbon dioxide (CO 2) corrosion. A crack-free laminar surface film was observed on the N80 oil tube steel under turbulent flow condition for 72 h at 80 °C with a carbon dioxide partial pressure of 0.5 MPa. The surface film was composed mainly of a complex carbonate (Fe, Ca)CO 3 and of a limited amount of α-FeOOH. The complex carbonate produced under the condition of this study was unstable and partially decomposed into α-FeOOH in desiccated air. The extending of the corrosion testing time and the formation of complex carbonate both contributed to the enhanced stability of the surface film.