Water splitting by Sulfur–Iodine (S–I) cycle is one of the promising thermochemical processes for hydrogen production due to its high efficiency. The decomposition of H₂SO₄ to produce SO₂ is the reaction with the highest energy demand in the S–I cycle and it shows a large kinetic barrier. Sulfuric acid ishighly corrosive and its endothermic decomposition needs elevated temperatures (>800 ^ºC). Henceforth, before the scale-up of the process plant there is a need to explore various materials of construction under very harsh acidic environments and phase changing conditions. Corrosion studies on some of the possible materials of construction (SS-304, SS-310, SS-316, Inconel-800, Alloy-20, Inconel-600, Incoloy-800H, Hastelloy C-276) were performed in detail and the most corrosion resistant material is suggested for the construction of sulfuric acid decomposition unit. The studies were performed at low temperatures (60^ºC and 120^ºC) as well as at high temperatures (700^ºC, 800^ºC and 900^ºC). The corrosion rates were determined using weight loss method at low as well as high temperature and by using electrochemical method at low temperature (80^ºC). The phase changing condition was more severe and resulted in higher corrosion rate. Hastelloy C-276 showed the least corrosion rate.