ANALYTICAL METHODS FOR STUDYING CATHODIC HYDROGEN CHARGING INTO METALS UNDER COMPETITIVE ADSORPTION CONDITIONS

This paper describes the IPZ (Iyer, Pickering, Zamanzadeh) and IPZA (Iyer, Pickering, Zamanzadeh, Al-Faqeer) methods for analyzing the steady state hydrogen permeation data obtained by the well known electrochemical hydrogen permeation technique. They yield the (i) individual rate constants of the hydrogen evolution reaction (HER), k(1) and k(2), the hydrogen surface coverage, theta(H), and the hydrogen concentration in the metal at the charging side of the membrane, C-H degrees, and (ii) the kinetic-diffusion rate constant, k, the absorption rate constant, k(abs), and the desorption rate constant, k(des), of the hydrogen absorption reaction (HAR). The IPZA also yields the surface coverage of a second adsorbent, theta(A). Data for iodide ion adsorption is presented in this paper. The IPZA-iodide coverage values, theta(1), were in reasonable agreement with theta(1)- values determined by two other independent methods: electrochemical quartz crystal microbalance (EQCM) and the estimated corrosion current density (i(corr)). This agreement is a powerful documentation of the validity of the underlying framework of the IPZ and IPZA analysis methods.