The permeability coefficients and effective diffusivities were measured at 49 to 506C by using an ultra-high vacuum monopole gas analyzer technique. The permeation activation energies for H and D were almost equal, at 8.52 and 8.78kcal/mol respectively, and the corresponding activation energies for diffusion were 1.69 and 1.93kcal/mol. The solubilities which were calculated from the permeability data and effective diffusivity measurements were therefore also equal. An analysis of the permeability coefficients and effective diffusivities revealed an isotope effect that was slightly greater than the classical ratio (1.41) at low temperatures, but gradually decreased - with increasing temperature - to a value which was just less than 1.41. The overall permeation results could be described by:

H:     P (atoms/cm s atm½) = 2.53 x 10-17 exp[-8.52(kcal/mol)/RT]

D:     P (atoms/cm s atm½) = 2.25 x 10-17 exp[-8.78(kcal/mol)/RT]

while the effective diffusivities were described by:

H:     D (cm2/s) = 1.61 x 10-3 exp[-1.69(kcal/mol)/RT]

D:     D (cm2/s) = 1.52 x 10-3 exp[-1.93(kcal/mol)/RT]

Hydrogen and Deuterium in Iron, 49–506°C. N.R.Quick, H.H.Johnson: Acta Metallurgica, 1978, 26[6], 903-7