Corrosion behavior of 304 stainless steel in supercritical water

Supercritical water (SCW) has strong reactivity and the ability to fuse non-polar substances, but it requires higher corrosion resistance of structural materials. To select reliable candidate materials for a supercritical water system, this study investigated the corrosion behavior of 304 stainless steel (304 SS) in supercritical water (798 K/ 24 MPa). After soaking 304 SS in supercritical water for 200 h, the oxidation kinetics, surface morphology, and element diffusion were studied by weight measurement, scanning electron microscopy (SEM), X-ray diffraction (XRD), energy dispersion spectroscopy (EDS) and X-ray photoelectron spectroscopy (XPS). The surface of 304 SS shows an isolated and discontinuous oxidation deposition. It is determined that the oxide layer is a single layer, mainly composed of Fe-Cr-rich spinel, with a small amount of magnetite attached to the surface of the oxide layer. Besides, the oxidation mechanism was also studied since some pores were found on the surface due to pitting.