The entry of H into monocrystals with (881), (771) and (661) faces was monitored during cathodic galvanostatic polarization in H2SO4 electrolytes which contained Cl ions. Large kinetic differences were found for permeation at low levels (less than 3.7 x 10-5wt%) of H in the crystal lattice. At higher levels, the permeation parameters began to exhibit a marked dependence upon structural changes in the membrane material. At chloride concentrations of less than 0.01M, the H diffusivity was estimated to range  from 1.2 x 10-8 to 2.3 x 10-8cm2/s. At chloride concentrations of about 0.1M, the H diffusivity increased to between 1.5 x 10-8 and 2.1 x 10-8cm2/s.

G.V.Khaldeev, T.F.Borisova: Elektrokhimiya, 1988, 24[5], 618-24. [Soviet Electrochemistry, 1988, 24[5], 579-85

Table 80

Diffusivity of H in Fe-Si