Simulation of a hydrogen permeation test on a multilayer membrane

To understand a metal susceptibility to Hydrogen Embrittlement (HE), it is important to quantify the diffusion of hydrogen through a metallic membrane. However the parameters directly accessible from electrochemical permeation experiments are the time required for a stream to be observed and the flux saturation corresponding to a steady state. The literature offers different models to obtain the diffusion coefficient from these curves. But this diffusion coefficient is not that of the membrane alone because it also takes into account the surface state and the kinetics of trapping. For some thicknesses of membrane and surface coatings (oxide) this approximation cannot be considered fair. We propose to simulate numerically the influence of the oxide thickness on the effective diffusion coefficient taking into account the trapped hydrogen.