The permeabilities, solubilities and effective diffusivities of H and D were measured at 9 to 73C by using electrochemical techniques. The activation energies for the permeation of H and D were essentially equal, with values of 8.36 and 8.57kcal/mol, respectively. The solubilities of the 2 isotopes were also equal. An evaluation of the steady-state fluxes and effective diffusivities indicated an isotopic effect of 1.8. This was considerably greater than the classical ratio of 1.41 (figure 2).

Hydrogen and Deuterium in Iron, 9-73°C. A.J.Kumnick, H.H.Johnson: Acta Metallurgica, 1977, 25, 891-5