ChemInform Abstract: The Corrosion Behavior of Silicon Carbide in 290 °C Water

Abstract

is studied as a function of pH and concentration of dissolved oxygen.

Effect of dissolved hydrogen on the corrosion behavior of chemically vapor deposited SiC in a simulated pressurized water reactor environment

“…The grain boundaries with higher interfacial energy are likely to be more susceptible to oxidation mediated by water molecules. The resulting oxide layer was not stable but readily dissolved into water under hydrothermal conditions, as has been found in many studies [23][24][25][26][27][28]. Thus, the facilitated oxidation reaction with water at grain boundaries seems to lead to preferential corrosion at those grain boundaries.…”

“…Although the specimens have rather rough surfaces because we did not apply fine polishing for preparation of the test specimens, the surface microstructure was hardly changed after corrosion tests for up to 210 d. Compared with the microstructures in Fig. 2 and the previous corrosion test results [23,[25][26][27][28], the dissolution of SiC was extremely limited. Preferential corrosion at grain boundaries or pitting corrosion was hardly observed within the test duration in this study because of the extremely low corrosion rate after control of the dissolved hydrogen.…”

“…In the cases when the SiC ceramics contained impurities (e.g., sintering additives or free Si phase) at grain boundaries, preferential corrosion along the grain boundary was observed [23,24]. However, the highly pure CVD SiC used in this study had clean grain boundaries.…”

“…These involve the fabrication of long, thin-walled tubes, the hermetic joining of end-cap seals, the capability to retain fission products, and management of corrosion under the conditions occurring during normal operation and during severe accident [14,[18][19][20][21][22]. Several reports have addressed the dissolution characteristics of SiC ceramics in high-temperature and high-pressure water [23][24][25][26][27][28]. In our previous studies concerning the corrosion of SiC [24,25], the corrosion resistance of SiC in water at 360 • C was strongly influenced by the fabrication method of SiC ceramics.…”

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“…Hirayama also reported the weight loss increased with increasing pH value, the weight loss in the oxygenated solution was more than that in the deoxygenated solution [26]. Verral reported that there was no significant interaction between SiC and Zircaloy-4 at 1273 K; at 1773 K there was a diffusionbased reaction to form ZrC and free SiC, but the SiC Zircaloy cladding interaction was no worse than the UO 2 -Zircaloy cladding interaction [25].…”