Determination of parameters in surface limited hydrogen permeation through metal membrane

Abstract

Hydrogen permeation through metal membranes at low upstream pressures is considered in the regime where the permeation rate is limited by the surface processes and not by diffusion in the bulk. The mathematical model for the hydrogen permeation through asymmetric membrane in the surface limited regime (SLR) is briefly introduced. For this model, we show that it is not possible to determine the unknown hydrogen-related membrane parameters by measuring the permeation flux through the membrane only in one direction. As an alternative to experiments on permeation in both directions, we describe an innovative and simple experimental technique that enables measurement of the permeation and outgassing rates of the membrane. All fluxes are determined from the upstream pressure change. For the proposed technique, we give a mathematical model and procedure that allows to extract all hydrogen-related membrane parameters from the experimental data without any fitting, solving of differential equations and without relying on the published parameters. The error of the obtained parameters introduced by the calculational procedure is only a few percents.