The permeability of H through intermetallic membranes was studied by using gas-permeation methods at 573 to 1223K. The effect of a third element (Cr, Fe, Zr) upon the retardation of H transfer, from the gas phase and into the bulk, was deduced from the dependence of the measured permeation flux upon the sample thickness. It was found that Zr enhanced, while Cr suppressed, the inhibiting effect of the surface. The most marked effect of Fe addition was to increase the grain-boundary brittleness in a H environment.

Surface Barrier for Hydrogen Permeability in Ni3Al - Influence of Cr, Fe and Zr. J.Cermak, V.Rothova: Intermetallics, 2001, 9[5], 403-8