Effect of Oxide Film on the Reduction of Hydrogen Permeation Rate in Stainless Steel

Characteristics of hydrogen permeation in the stainless steel 304 modified by either facing, ion sputtering, carbon coating or annealing were investigated in order to establish the safe hydrogen-energy-infrastructure using welding. A stationary hydrogen flux from the stainless steel surface was measured by using a system with an orifice. The pressure difference of the specimen was able to maintain constant by controlling the gas flow rate from the orifice in low pressure vessel. The hydrogen permeability was low in two cases of a thin stainless steel with fine facing and that annealed at 1370K for 2 hours. In these cases, the specimens’ surfaces were considered to play hydrogen trap role and to prevent from pairing hydrogen atoms. On the other hand, high hydrogen permeability was obtained in the case of Argon plasma cleaning a low-pressure-vessel side surface. These results suggest that oxide film on the specimens’ surface prevent hydrogen desorption.