The application of an elastic tensile stress to iron or steel membranes charged from one side with hydrogen in acid solutions is reported to increase the steady-state rate of hydrogen permeation.1-3 This increase is usually discussed in terms of Fick’s first law:
where JH is the flux of hydrogen through the membrane, D is the diffusion coefficient of hydrogen in iron, Δx is the membrane thickness, and Δc is the difference in concentration of hydrogen on input and output surfaces. The diffusion coefficient as determined in independent measurements (rise or decay transient) is found to be independent of stress. The concentration of hydrogen at the output surface is assumed, under the conditions of the experiments, to be vanishingly small; the concentration at the input surface is assumed to be equal to the lattice solubility, S, for hydrogen in...
