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Report No.

Corrosion resistance of structural materials in high-temperature aqueous sulfuric acids in thermochemical water-splitting iodine-sulfur process

Kubo, Shinji; Futakawa, Masatoshi; Ioka, Ikuo; Onuki, Kaoru; Yamaguchi, Akihisa*

Very harsh environments exist in the iodine-sulfur process for hydrogen production. Structural materials for sulfuric acid vaporizers and concentrators are exposed to high-temperature corrosive environments. Immersion tests were carried out to evaluate the corrosion resistance of ceramics and to evaluate corrosion-resistant metals exposed to environments of aqueous sulfuric acids at temperatures of 320, 380, and 460$$^{circ}$$C, and pressure of 2 MPa. The aqueous sulfuric acid concentrations for the temperatures were 75, 85, and 95 wt%, respectively. Ceramic specimens of silicon carbides (SiC), silicon impregnated silicon carbides (Si-SiC), and silicon nitrides (Si$$_{3}$$N$$_{4}$$) showed excellent corrosion resistance from weight loss measurements after exposure to 75, 85, and 95 wt% sulfuric acid. High-silicon irons with silicon content of 20 wt% showed a fair measure of corrosion resistance. However, evidence of crack formation was detected via microscopy. Silicon enriched steels severely suffered from uniform corrosion with a corrosion rate in 95 wt% sulfuric acid of approximately 1 gm$$^{-2}$$h$$^{-2}$$. Among the tested materials, the ceramics SiC, Si-SiC, and Si$$_{3}$$N$$_{4}$$ were found to be suitable candidates for structural materials in direct contact with the considered environments.



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Category:Chemistry, Physical



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