Investigation into the cause of leak in the pipe of the corrosion test apparatus of IS process

Tanaka, Nobuyuki ; Suwa, Hirokazu*; Furukawa, Tomohiro  ; Inagaki, Yoshiyuki

The thermochemical hydrogen production IS process utilizes corrosive chemicals such as sulfuric acid and hydriodic acid. Corrosion tests in IS process environments have been carried out to get the corrosion data of materials. In the corrosion test in sulfuric acid at 400C, the leak of sulfuric acid was observed in a pipe connected with a reflux condenser. The cause of the leakage is an important significant knowledge for the operation of the test apparatus. Therefore the cause was investigated. A through hole was detected in the pipe around the welding bead. By visual observation after cutting the pipe, the wall thickness of the pipe became thin at the inside welding bead around the through hole. In addition, EPMA showed that the inhomogeneous distribution of the constituent elements of the pipe was observed around the through hole. For these reasons, it is estimated that the lowering of the corrosion resistance by the sensitization at the welding caused the leakage.