Resistance to corrosion of silicon-based ceramic materials in suifuric acid containing environments for hydrogen production

Silicon based ceramic materials, such as silicon carbide and silicon nitride, are promising candidates for use in high-temperature components for the SI process. Four different materials were examined and found to oxidize in high-temperature sulfuric acid vapour. The oxidation product, silica (SiO ₂), appeared to strengthen the material by blunting cracks and was stable in the vaporous sulfuric acid environment. Material recession and evidence of pitting was seen after exposures at elevated temperatures in liquid sulfuric acid, under pressure, but corrosion rates were still an order of magnitude lower than for metallic materials. Silicon nitride specimens were weakened by exposure to boiling, liquid sulfuric acid, which suggests that corrosion may be accelerated in liquid sulfuric acid or at the triple point between the substrate, liquid, and vapour. Additional experiments and characterization will be performed to understand this behavior.