Hydrogen permeation through vanadium and the effect of surface impurity layer on it

Hydrogen permeation through vanadium was investigated with a high vacuum system over the hydrogen pressure range 2 x 10-1 to 6.5 x 104 Pa and the temperature range 578-1072 K. For the three specimens, the permeation rate was linearly proportional to the hydrogen pressure in the low pressure region, while the pressure dependence gradually changed to a parabolic one with increasing pressure. The activation energy for hydrogen permeation through vanadium increased from 30 to 74 kJ x mol-1 as the hydrogen pressure was decreased. The hydrogen permeation rates of the three specimens were different from each other and this behavior was explained by the oxide barrier model. By the AES measurement, the surface oxide layer was identified to exert a barrier effect on the hydrogen permeation rate of the vanadium specimen. (orig.)