By using combined electrochemical and gas-volumetric techniques, a study was made of the permeation of H through Fe specimens of various degrees of purity. The results indicated (table 12) that O concentrations of 150 to 400ppm and Ni concentration of up to 0.04wt% had no measurable influence upon the H diffusion coefficients; as calculated from the time-dependence of the permeability data. However, Ni concentrations above 0.04wt% - as well as increasing concentrations of other impurities - resulted in a decreased diffusion coefficient. Within the range of I = 0 to 0.5wt% of impurities, the diffusivity of H at 25C could be described by:

D (cm2/s) = 4.3 x 10-6 exp[-4.8 I(wt%)]

W.Dresler, M.G.Frohberg, H.G.Feller: Zeitschrift für Metallkunde, 1972, 63[2], 94-8

 

Table 12

Apparent Diffusivities of H in Fe of Various Degrees of Purity at 25C

 

Material

D (cm2/s)

high-purity (4N85) Fe

4.08 x 10-6

electrolytic (2N87) Fe, 400ppmO

2.8 x 10-6

electrolytic (2N87) Fe, 150ppmO

2.85 x 10-6

Armco (2N5) Fe

3.9 x 10-7

high-purity Fe, 0.04wt%Ni

4.56 x 10-6

electrolytic Fe, 0.09wt%Ni

1.34 x 10-6

high-purity Fe, 0.15wt%Ni

1.22 x 10-6

electrolytic Fe, 0.5wt%Ni

1.14 x 10-6

high-purity Fe, 0.9wt%Ni

9.8 x 10-7

electrolytic Fe, 1.7wt%Ni

8.07 x 10-7

electrolytic Fe, 2.5wt%Ni

8.2 x 10-7