By using a time-lag technique, an investigation was made of H permeation through 18Cr-8%Ni steel plates as a function of the H pressure (0.1 to 30atm) at the entry surface, the temperature (300 to 800C), and the membrane thickness (0.0252 to 0.2475cm). The permeabilities were strongly dependent upon the H pressure, and this was attributed to aresistance to flow at the membrane surface, rather than to a concentration-dependent diffusivity of H in the steel (table 90). Overall, the data could be described by:

D (cm2/s) = 0.44 exp[-12.5(kcal/mol)/RT]

J.R.Phillips, B.F.Dodge: American Institute of Chemical Engineers Journal, 1968, 14[3], 392-7

 Table 90

Permeation and Diffusion of H in 18Cr-8%Ni Steel

 

Thickness (cm)

Temperature (C)

H2 (atm)

P (cm3/min atm½)

D (cm2/s)

0.1011

603

1.03

1.3 x 10-3

3.3 x 10-4

0.1011

603

10.9

1.2 x 10-2

3.3 x 10-4

0.1011

395

1.01

2.0 x 10-4

3.6 x 10-5

0.1011

395

10.2

7.5 x 10-4

3.6 x 10-5

0.1011

395

29.1

2.0 x 10-3

3.6 x 10-5

0.2475

398

1.04

5.9 x 10-5

3.6 x 10-5

0.2475

398

10.1

2.4 x 10-4

3.6 x 10-5

0.2475

398

30.4

9.1 x 10-4

3.6 x 10-5

0.1003

302

1.04

5.0 x 10-5

7.9 x 10-6

0.1003

302

30.1

8.0 x 10-5

7.9 x 10-6