Electrochemical permeation tests enable the experimental determination of the diffusion coefficient of a metal. To get a better understanding and a correction of experimental measures, the effects of hydrogen trapping on the diffusion of hydrogen through a metallic membrane were investigated by simulating a FEM model. The trap binding energy ΔET ranged from −0.1 to −0.32eV, the density of traps ranges between 10−4 and 100mol/m3, and the thickness of the membrane fluctuated from 100μm to 1mm. It appeared that the effective diffusion coefficient extracted from desorption flux data of a single membrane was not influenced by its geometry and depended upon both the density of trapped hydrogen and the trap binding energy such as the apparent diffusion coefficient implemented in the code. Thus, no scale effect was detected. In the other hand, the effective sub-surface concentration evaluation using usually Fick’s laws did not correspond directly to hydrogen concentration in the membrane. Analytical equations to solve the problem to extract erroneous data (diffusion coefficient and hydrogen concentration) to the experimental measurements of the flux vs time curves were proposed.

Computational Analysis of Geometrical Factors Affecting Experimental Data Extracted From Hydrogen Permeation Tests I – Consequences of Trapping. J.Bouhattate, E.Legrand, X.Feaugas: International Journal of Hydrogen Energy, 2011, 36[19], 12644-52