The primary purpose of this study is to examine effects of density and of density-related physical properties of water on corrosion behavior of alloys in supercritical aqueous solutions. Corrosion experiments were done on three kinds of Ni-base alloys and a type 316 stainless steel in an aqueous solution containing 0.01mol/kg-H2SO4 and 0.025mol/kg-O2 at 400°C under various applied pressures from 25MPa to 60MPa. Corrosion tests were performed also under a subcritical condition, at 360°C/25MPa, for the Ni-base alloys for comparison with the results under supercritical conditions. Corrosion rates of the Ni-base alloys at 400°C significantly increased with increased pressure. Corrosion rates of each Ni-base alloy were uniquely correlated with either density or dielectric constant of the water including both the supercritical conditions and the subcritical condition. Type 316 stainless steel showed quite good corrosion resistance at 400°C both at 30MPa and at 40MPa. However, intergranular corrosion occurred and the corrosion rate increased by more than two orders of magnitude when pressure was increased to 60MPa. The results demonstrated importance of density and density-related physical properties of water on corrosion behavior of alloys in pressurized hightemperature water.
ASJC Scopus subject areas
- 化学 (全般)