Precise measurements of H permeation through high-purity material were performed by using a gaseous permeation technique, and H pressures of between 0.001 and 0.1MPa, at temperatures of between 420 and 1100K. It was found that the permeability and diffusivity could be described by:

P (mol/m s MPa½) = 2.88 x 10-5 exp[-32.12(kJ/mol)/RT]

 D (m2/s) = 6.04 x 10-8 exp[-6.99(kJ/mol)/RT] 

Permeation was reduced by sample deformation, and this change was attributed to H-trapping by lattice imperfections that were produced by the deformation. Both the permeability and diffusivity were reduced by surface oxidation.

T.Tanabe, Y.Yamanishi, S.Imoto: Transactions of the Japan Institute of Metals, 1984, 25[1], 1-10

Table 61

Parameters for Diffusion and Permeation of H in Fe