Tham khảo tài liệu 'materials for the hydrogen economy (2009) part 5', kỹ thuật - công nghệ, cơ khí - chế tạo máy phục vụ nhu cầu học tập, nghiên cứu và làm việc hiệu quả | 96 Materials for the Hydrogen Economy FIGURE Cross-section through the surface film that formed on a Saramet 23 sample exposed to sulfuric acid at 375 C. TABLE Corrosion Rate of Si-Based Ceramics and High-Si Steel in Concentrated H2SO4 at High Temperature H2SO4 Acid Concentration and Temperature 95 wt 460 C 85 wt 380 C 75 wt 320 C 100 h 1 000 h 100 h 100 h SiC 0 0 Si-SiC 0 NA 0 Si3N4 0 0 0 Fe-20 Si NA NA Fe-Si annealed 0 0 Ni-Cr-Si steel NA 5 17 h Note Original corrosion rate g m2h from the reference is used. Minus sign indicates weight gain. Construction materials capable of handling H2SO4 vapor were studied extensively during the early stages of the S-I cycle development as it was thought to be the most critical materials issue of the cycle. Because of the high operating temperature involved materials candidates were chosen from those that derive their strength from solid-solution strengthening instead of precipitation hardening as overage conditions can lead to a decrease in strength. Different researchers have come to a similar conclusion that steel with a high Ni-Cr content is most suitable for the decomposition reaction especially when the operation temperature is above 850 C. At this temperature it was found that corrosion due to H2SO4 vapor is similar to that in air 22 and thus many qualified high-temperature engineering alloys can Thermochemical Hydrogen Production 97 be suitable. Alloys that have been tested in this environment include Incoloy 800H AISI310 Inconel 600 stainless 304 a 70 Fe-10 Ni-18 Cr alloy 14 22-26 The high Cr content in all these alloys helps to passivate the metal surface. Among all the different candidates Incoloy 800H has shown the best performance with a corrosion rate of less than 100 pm yr after a 9 000-h test at 900 C. AISI310 was judged to be applicable to lower-temperature Construction materials for vaporization and decomposition of H2SO4 .
