The diffusivity of H in annealed and cold-rolled samples, under varying .

cathodic current densities, was studied at 279 to 335K by using electrochemical techniques. The results could be described by:

annealed:     D (cm2/s) = 1.04 x 10-3 exp[-5.1(kcal/mol)/RT]

cold-worked:     D (cm2/s) = 8.21 x 10-4 exp[-5.3(kcal/mol)/RT]

In neither type of specimen did the activation energy for diffusion depend upon the H content beneath the cathodic surface. The activation energy in the case of annealed material was equal to 21.48kJ/mol. The corresponding value for cold-rolled material was slightly larger. The diffusion coefficient in the latter case was lower than that for annealed material, and increased with increasing H content.

Y.Sakamoto, N.Tabaru: Journal of the Japan Institute of Metals, 1981, 45[10], 1048-55