The diffusion of H in group-V transition metals was measured, at 500 to 1100C, using absorption methods. The data obtained at high temperatures agreed well with the published results of resistivity and other studies. They did not agree with data which had been obtained at moderate temperatures by using the same absorption method. Below some critical temperature (540 to 700C), the values of the diffusion coefficient deviated downwards from the linear Arrhenius plot (figure 37). This deviation was attributed to the effect of surface layers, such as oxide films, which affected H absorption by the metal. The diffusion coefficient of H in V was decreased by alloying Cr, Fe or Nb, but was increased by adding 40at%Ti. Variations in the pre-exponential factor and the activation energy, as a function of alloy concentration almost parallelled that of the electric specific heat coefficient. It was concluded that the screening of protons by electrons played an important role in diffusion, as with the case of H solubility.

Diffusion of Hydrogen at High Temperatures in the Group V Transition Metals and Alloying Effect on the Diffusion. T.Eguchi, S.Morozumi: Journal of the Japan Institute of Metals, 1977, 41[8], 795-802