Corrosion test of metallic materials in high temperature acidic environments of IS process

Tanaka, Nobuyuki ; Nagae, Masahiro*; Ioka, Ikuo ; Iwatsuki, Jin ; Kubo, Shinji ; Onuki, Kaoru

The Thermochemical water-splitting cycle IS process constitutes severe environments to the materials of construction because of the corrosive chemicals. This paper discusses corrosion resistance of novel metallic materials in high temperature sulfuric and hydriodic acid. As for the sulfuric acid environment, corrosion resistances of MoN, Mo-Ta-N, and Mo-Cr-N alloys were examined. The experiments were performed for the duration of 5 hour in 90wt% sulfuric acid at 300C. Although no material showed satisfactory corrosion resistance (ca. 1.5 mm/y in the case of MoN), the addition of Ta or Cr was found to be effective to improve the corrosion resistance. As for the hydriodic acid environment, corrosion resistance of Nb-W alloy was examined by immersing the test pieces for up to 100 hours in the test solutions of 200C. It was observed that the corrosion rates lowered with the progress of immersion time and reached to a stable value of lower than 0.1 mm/y.