Effects of Hydrogen Peroxide on Intergranular Stress Corrosion Cracking of Stainless Steel in High Temperature Water, (V). Characterization of Oxide Film on Stainless Steel by Multilateral Surface Analyses.

Abstract

Abstract The difference in electrochemical corrosion potential of stainless steel exposed to high temperature pure water containing hydrogen peroxide (H2O2) and oxygen (O2)is caused by differences in chemical form of oxide films. In order to identify differences in oxide film structures on stainless steel after exposure to H2O2 and O2 environments, characteristics of the oxide films have been examined by multilateral surface analyses, e.g., X-ray diffraction (XRD), Rutherford back scattering spectroscopy (RBS), secondary ion mass spectroscopy (SIMS) and X-ray photoelectron spectroscopy (XPS). Preliminary characterization results of oxide films confirmed that the oxide film formed under the H2O2 environment consists mainly of hematite (α-Fe2O2), while that under the O2 environment consists of magnetite (Fe3O4). Furthermore oxidation at the very surface of the film is much more enhanced under the H2O2 environment than that under the O2 environment. It was speculated that metal hydroxide plays an important role in oxidation of stainless steel in the presence of H2O2. The difference in electric resistance of oxide film causes the difference in anodic polarization properties. It is recommended that several anodic polarization curves for specimens with differently oxidized films should be prepared to calculate ECP based on the Evans diagram. KEYWORDS: BWR type reactorshydrogen peroxideoxide filmstainless steelssurface characterizationhematitemagnetiteelectrochemical corrosionintergranular corrosionclacking