Abstract
Many kinds of advanced cermaics, which have been recently developed, are considered to have much possibility for engineering applications as structural materials in high temperature water environments. In the previous report, fundamental corrosion behaviors of 14 kinds of sintered polycrystalline ceramics in 290°C high purity water with or without dissolved oxygen were clarified. In the present study, pH and immersion time dependences of corrosion behaviors of sillicon carbide and stabilized zirconia were discussed. Silicon carbide showed high corrosion resistivity, and the corrosion rate increased at higher pH and oxygenated solution. Time dependence of corrosion weight loss obeyed a power law with the power of 0.7 to 1.3 depending on pH value. Surface silica layer formation was not detected by X-ray diffractometry and Auger electron spectroscopy. These results suggest simultaneous hydrothermal oxidation and dissolution, rather than two step oxidation and dissolution with a protective silica layer. Stabilized zirconia with 6mol% and 8mol% of yttria also showed excellent corrosion resistance, especially the corrosion weight loss for 8mol% yttria stabilized zirconia was below the detection limit in oxygen-free neutral and pH 10 solution.
