The diffusivity of H in pure monocrystalline material was measured at 230 to 300K. The Permeation was determined by using an electrochemical technique. The diffusion data were described by the relationship:

D (m2/s) = 1.1 x 10-7 exp[-6.7(kJ/mol)/RT]

This result was in agreement with published high-temperature data. In the case of polycrystalline material, the diffusion data could not be described by using a single Arrhenius expression. At 298K, the diffusion coefficient was equal to 7 x 10-9m2/s; and this value was independent of the grain size and specimen thickness.

H.Hagi, Y.Hayashi, N.Ohtani: Transactions of the Japan Institute of Metals, 1979, 20[7], 349-57