Chemical stability of Cr2O3 in high temperature water is one of the most important factors for corrosion resistivity. In this study, chemical stability of Cr2O3 was investigated in high temperature water up to critical region. From the immersion tests of the Pt specimens with Cr2O3 film formed by metal organic chemical vapor deposition, following conclusions were obtained. In air-saturated water and DO (dissolved oxygen) 400 ppb water at 623 K, Cr2O3 is oxidized and Cr(VI) ions are stable. In the deaerated solution, metal chromium is stable. Therefore, Cr2O3 is chemically stable under the condition of DO concentration less than a threshold between 0 and 400 ppb. At 723 K, Cr2O3 is chemically stable under the condition of DO concentration up to 400 ppb. The threshold concentration is more than 400 ppb. After the immersion tests in the deaerated solution and DO 400 ppb water at 723 K, weight of Cr2O3 was decreased, but crystallinity of Cr2O3 was increased. Possible mechanism of crystallinity growth was discussed. In situ Raman spectroscopy of Cr2O3 in suspension was conducted at 573 K. It is tentatively concluded that Cr2O3 is stable in DO 8000 ppb water at 573K.

Subject
X-ray diffraction, Stability, Immersion tests, Water, Chromium, Raman spectroscopy, Oxide films, Chromium oxide, Solutions, Film formation, Metals, Immersion, High temperature
Keywords:
corrosion, supercritical water, chromium oxide, MOCVD, redox condition, Raman spectroscopy
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2007
Association for Materials Protection and Performance (AMPP)
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