Abstract
A thermochemical water-splitting iodine-sulfur process (IS process) is one of candidates for the large-scale production of hydrogen using heat from nuclear energy. Severe corrosive environment which is thermal decomposition of sulfuric acid exists in the IS process. To achieve an industrialization of massive hydrogen production system, one of the key factors is the development of structural materials for the severe corrosive environment. A hybrid material with the corrosion-resistance and the ductility had been made by a silicon powder plasma spraying and laser treatment. To confirm the applicability of the hybrid material as the structural material, corrosion tests of the hybrid materials had been performed in 95 mass% and 47 mass% boiling sulfuric acid. The corrosion resistance of specimen in the condition of 95 mass% boiling sulfuric acid had been excellent. This was attributed to the formation of SiO2 on the surface. To confirm the production characteristics as a container using the hybrid material, the container which has a welded part, a chamfer, a curved surface had been experimentally made. A configuration of the container had been 150mm inside diameter, 120mm in height and 6mm in thickness. The substrate of the container made of Hastelloy C276® superalloy had included TIG weld part. To improve the corrosion resistance of the container, pre-oxidation was performed at 800°C for 100 hours in air. There was no detachment of the plasma spraying and laser treated layer on the base metal and the welded part. The pre-oxidized container using hybrid technique was prepared for the corrosion test in boiling sulfuric acid to evaluate the characteristics of the container.
