The diffusion of H in 4N-purity material was described by the relationship:

D (m2/s) = 4.58 x 10-6 exp[-37.03(kJ/mol)/RT]

These data reflected the diffusion of atomic H in the Al lattice. When the specimens were melted, and re-solidified in metal moulds, the diffusivity decreased; with the difference being larger at lower temperatures. This change explained on the basis that the diffusivity was a function of the total number of voids which were formed by H gas during solidification.

M.Ichimura, M.Imabayashi, M.Hayakawa: Nippon Kinzoku Gakkaishi, 1979, 43[9], 876-83

Table 29

Diffusivity of H in Al