By measuring out-diffusion from samples which had previously been loaded with H, the H diffusion coefficients in binary alloys were determined. They were found for the α-phase of each alloy, for temperatures of between 25 and 300C, and could be described by:

log[D] = -3.635 + 0.014Cr - (1486 + 44Cr)/4.575T(K)

when the contents of the alloying elements were expressed in mol%. The additions decreased the H diffusion coefficient. The diffusion-retarding effect of the alloying element increased with decreasing temperature. The overall temperature expression for the diffusion of H in Fe:

log[D] = -3.67 - 1438/4.575T

was obtained by extrapolating the above equation to 0% alloying element concentration. This result agreed quite well with the most likely value for the lattice diffusion of H; as extrapolated from measurements made at high temperatures.

H.J.Koenig, K.W.Lange: Archiv für Eisenhüttenwesen, 1975, 46[10], 669-75