Effect of EB treatment on permeation enhancement of palladium-free hydrogen purification membrane of SUS316L

As the hydrogen society progresses, Fuel Cell Vehicles (FCVs) are rapidly becoming more widespread. Metal hydrogen permeable membranes, which are the essential parts of the hydrogen fuels for polymer electrolyte fuel cells (PEFCs), require an alternative material to palladium from a cost point of view. Austenitic stainless steel, which is low cost, corrosion resistant, and easy to prepare for manufacture, has been considered unsuitable as a hydrogen permeable membrane because its passive film inhibits hydrogen permeation. However, destabilization of the surface oxide film and thin processing can be expected to improve its permeability. In this work, 18mass%Cr-8mass%Ni-2mass%Mo-Low Carbon (0.02mass%) stainless steel alloy (SUS316L) foils were irradiated with electron beam (EB) in a nitrogen atmosphere to investigate the effect of EB treatment on hydrogen permeability. The diffusion coefficient of hydrogen in the passive layer on the surface of stainless steel irradiated at 250 kV and 600 kGy was calculated to be promoted about 8 times compared to the untreated one, by applying Schmitz's multilayer hydrogen diffusion permeation model. Based on the results obtained, partial destabilization of the surface oxide film by irradiation treatment is suggested.