An analysis of H transport showed that both trapping and short-circuit diffusion occurred, and that both had small but significant effects upon permeation, evolution and absorption. Both effects appeared to be associated mainly with the dislocation sub-structure of Ni. Data on D permeation and T absorption and out-gassing in pure polycrystalline Ni (annealed or heavily cold-rolled), were combined with earlier measurements of the diffusivity and solubility of H isotopes to give the relationships:

diffusivity:     D (m2/s) = (7.0 x 10-7)/√M exp[-39500/RT]

solubility:     S (mol/m3) = 1.1 x 103 exp [-15800/RT]

permeability:     P (mol/s MPa½) = (7.9 x 10-4)/√M exp[-55300/RT]

Hydrogen Diffusion and Trapping in Nickel. M.R.Louthan, J.A.Donovan, G.R.Caskey: Acta Metallurgica, 1975, 23[6], 745-50

Table 107

Diffusion of H in Ni-Based Alloys