In the sulfur-iodine thermochemical cycle, hydrogen iodide (HI) gas is catalytically decomposed into hydrogen and iodine gases at around 450°C. Development work has been on going to identify and qualify construction materials that can be used for the fabrication of heat exchanger and other process components. A number of candidates have been screened via immersion in the decomposition environment in excess of 100 hours. Hastelloys C-22, C-276, B2 and B3 have been found to have the lowest general corrosion rate among the common engineering materials tested. To qualify these materials for use, their stress corrosion behavior was investigated. Their susceptibility to stress corrosion cracking was studied through testing of C-ring and U-bend specimens. No crack has been observed in the specimens after 1000 hours of testing. To probe their vulnerability to crack growth, wedged loaded pre-cracked double cantilever beam specimens have been immersed in the gaseous environment and this will provide a stress intensity factor of the various Hastelloys. This talk will present a summary of the material screening work in addition to stress corrosion test results from the Hastelloy specimens tested. This work was supported by the UNLV under RF-05-HTHX-001.

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