CORROSION OF SILICON CARBIDE IN GASES AND ALKALINE MELTS

The corrosion behavior of sintered SiC in gaseous environments and alkaline melts was investigated at 900°C. In oxidizing atmospheres such as normally exist in a gas turbine, SiC forms a dense coherent surface film of SiO2 which is not corroded by thin layers of condensed sodium sulfate. However, under some conditions, especially when very low oxygen pressures are maintained at the SiC surface or when basic salt melts or slags containing carbonaceous material are present, rapid corrosion of the ceramic can occur. On the other hand, SiC is inert in pure N2, H2, or H2-H2S mixtures at 900°C. These different modes of behavior are discussed in the context of possible high- temperature applications of SiC ceramics.