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:

Fe-Co:     log[D] = -3.723 - 0.002Co - (1452 + 29Co)/4.575T(K)

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

Fe-Mn:    log[D] = -3.625 - 0.032Mn - (1491 + 23Mn)/4.575T(K)

Fe-Ni:     log[D] = -3.512 + 0.024Ni - (1651 + 112Ni)/4.575T(K)

when the contents of the alloying elements were expressed in mol%. All of the additions decreased the H diffusion coefficient. Within the concentration range which was investigated, Ni had the greatest effect while the effect of the other elements decreased in the order: Mn, Co, Cr. The diffusion-retarding effect of the alloying elements increased with decreasing temperature. The concentration-dependence upon Ni was the one which increased most with decreasing temperature. With regard to the other alloying elements, this increase declined in the order: Cr, Co, Mn. The overall temperature expression for the diffusion of H in Fe:

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

was obtained by extrapolating the above equations 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