Determination of the Rate Constants of Hydrogen Absorption into Metals

Hydrogen absorption into iron (steel) membranes was studied using an electrochemical hydrogen permeation technique. The Iyer, Pickering, and Zamanzaden analysis of the measured steady‐state hydrogen permeation rates, obtained for different membrane thicknesses, gives the rate constants of hydrogen absorption, , and desorption, , in addition to those quantities which can be obtained from data for a single membrane thickness: i.e. , the hydrogen surface coverage, , exchange current density, , rate constants, and , of the hydrogen evolution reaction, and the important composite quantity called the kinetic‐diffusion constant, , where L is the membrane thickness and D is the diffusivity of hydrogen within the metal. The product of k and determines the steady‐state permeability of hydrogen within the metal. For large D and/or small L , , and the hydrogen permeation process is under surface control. From the analysis, we obtained and for iron in acidic sulfate solution.