Corrosion behaviour of different metallic materials under supercritical carbon dioxide at 550°C and 250 bars

In the framework of a new generation of nuclear reactors, typically Sodium Fast Reactors, supercritical carbon dioxide with a Brayton cycle (at 550°C and 250 bars) is identified as a promising energy conversion system to replace the traditional steam generators. Nevertheless, the long-term integrity of the heat exchanger structure in this environment has to be proven over at least 20 years. In this purpose, the corrosion behaviour of different metallic materials in static carbon dioxide at 550°C and 250 bars is studied: one 9wt% Cr ferrito-martensitic steel (T91) and several austenitic steels. The first results about the nature of the corrosion product, their morphology and their kinetic of formation revealed through surface analyses such as Glow Discharge Optical Emission Spectroscopy, Scanning Electronic Microscopy, Wavelength-Dispersive Spectroscopy and X-Ray Diffraction are shown. A corrosion mechanism of the different steels is proposed and the most promising materials for heat exchanger applications revealed