Electrochemical aspects of hydrogen in metals

Abstract

This is a review of the electrode kinetics of the hydrogen evolution reaction and the entry of electrolytic hydrogen into metals as it affects hydrogen embrittlement. Basic electrochemical parameters (for example, exchange current density, activation and concentration polarization and coverage) are described for the determination of a rate and mechanism for the hydrogen evolution reaction. Hydrogen coverage dependence on overpotential and current is discussed with reference to the Langmuir adsorption isotherm. Reactions responsible for the electrolytic production of hydrogen in aqueous solutions are described for corrosion processes that occur in occluded regions on or below the surface of the metal. Hydrogen adsorption-absorption processes and electrochemical hydrogen permeation test techniques for the determination of the susceptibility of metals to internal hydrogen embrittlement are presented.