An electrochemical method was used to study the permeation of H and D through membranes of 4N6-purity. The measurements were performed at 10 to 60C, for an input gas pressure of 0.1MPa. Diffusivities were deduced from the build-up and decay transients. The activation energy for diffusion was equal to 7.05kJ/mol for H, and to 8.60kJ/mol for D. The DH/DD ratio was found to be temperature-dependent; being equal to 1.8 at 60C and 2.05 at 10C. It was also greater than the square root of the mass ratio, and much greater than the value of 1.2 which was observed in high-temperature measurements.

Permeability, Diffusivity, and Solubility of Hydrogen and Deuterium in Pure Iron at 10 to 60°C. W.Raczynski: Physica Status Solidi A, 1978, 48[1], K27-30

Figure 2

Diffusivity of Isotopes in Fe

(open squares: H, filled squares: D)