Water splitting through thermochemical processes offers the potential for clean, efficient and cost-effective large scale production of hydrogen. Among the different thermochemical processes, the General Atomics Sulfur-Iodine (SI) cycle is a prime candidate as it offers a highly efficient process that can be achieved under practical reaction environments which helps to keep the final cost of hydrogen down. The SI cycle consists of three separate sections: 1) the Bunsen reaction section which produces sulfuric acid and hydriodic acid(HI) by reacting water with iodine and sulfur dioxide; 2) the oxygen generation section in which sulfuric acid is decomposed into sulfur dioxide, oxygen and water and; 3) the hydrogen generation section in which HI is decomposed into hydrogen gas and iodine. The oxygen generation temperature can run as high as 900ºC and hydrogen generation pressure can reach more than 5MPa. Furthermore, many of the chemicals employed within the cycle are strong oxidizers and iodide is a strong complexing agent. Such conditions create an extremely corrosive environment and impose severe demand on materials used to build the various structures within the cycle. In order to realize a stable, safe and economically viable hydrogen production plant, careful selection of materials and designs employed to manufacture the chemical reactors, heat exchanges and other components must be taken. This presentation will outline the construction materials requirements for the different process sections within the SI cycle and a review of some of the methodologies that have been developed to identify suitable corrosion resistant materials will be given. A review of past and up to date results and a future materials development roadmap will also be presented.