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Pitting corrosion in CVD SiC at 300°C in deoxygenated high-purity water

“…More study would be needed to determine the absolute rate kinetics of this loss and the exact determination of the mass loss was not made here, although it is small. The results observed here are consistent with reduced corrosion rates in water with low oxygen concentrations compared with studies in water without oxygen control as also observed by others [16][17][18][19].…”

“…Mass loss was higher for SiC containing free Si compared to higher purity CVD SiC and it was hypothesized that similar surface dissolution of silicon via soluble hydroxides was occurring as for Hirayama et al [17]. A similar study using reaction-bonded SiC (RBSC) found much higher corrosion rates for RBSC compared to CVD SiC at 633 K [19].…”

“…The research of Tomozawa and Doremus on the chemistry of silica in water is relevant here in identifying water-silica reactions [20][21][22][23][24][25]. Kim et al exposed CVD b-SiC to static distilled water at 633 K for up to 240 h and observed parabolic mass loss and preferential surface corrosion along CVD columnar grain boundaries [16,19]. Mass loss was higher for SiC containing free Si compared to higher purity CVD SiC and it was hypothesized that similar surface dissolution of silicon via soluble hydroxides was occurring as for Hirayama et al [17].…”

“…The observation of pitting corrosion in SiC materials for hightemperature corrosion processes, T > 1273 K, has been documented for molten salts [27,28] but no literature exists, to the best of our knowledge, for pit formation in pure water at 573 K [16][17][18][19]. However, there are reaction mechanisms that could account for the formation of pits in b-SiC at any temperature [17,29].…”

“…The swelling data is rather complete for b-SiC in the temperature range of 300-1730 K [6,7]. But, corrosion data of high-purity b-SiC in water is somewhat lacking for temperatures in the vicinity of 573 K, the operating temperatures of many water-cooled reactors [16][17][18][19].…”