Steel used in immersed conditions may undergo the generation and absorption of atomic hydrogen possibly being trapped in the metal lattice and causing structural material issues. Hence, it is of fundamental importance to develop a model able to predict how the hydrogen interacts with the metal, both at the surface and in the bulk of the material.
Hydrogen diffusion is generally investigated using the Devanathan-Stachurski cell. In this cell, atomic hydrogen is amperostatically generated through water reduction at one side of a metal membrane. Subsequently, part of the hydrogen is absorbed and free to move through the alloy. Conclusively, it is oxidized at the other side of this membrane, where a current is measured resulting from the imposed anodic potential. These recorded currents provide the diffusion coefficient and give an indication on hydrogen trapping in the metal alloy. The kinetics of the hydrogen-related reactions taking place at the two surfaces are ordinarily overlooked and usually focus is mainly on the diffusion phenomena alone. In the present work, the importance of surface effects on the oxidation current collected from the Devanathan-Stachurski cell is shown, which have significant influence on the current measured and its interpretation. In particular, we demonstrate how the kinetics of hydrogen absorption at the entry side and desorption at the exit side of the membrane can drastically affect the shape of the output current obtained. This can have an influence on the quantification of parameters such as trapping and apparent diffusion coefficients, highlighting a possible misinterpretation of the results. Also, the concentration profile of hydrogen in the membrane is strongly influenced. A model of the abovementioned cell was created, able to predict hydrogen generation, adsorption, absorption, diffusion, trapping and desorption through electrochemical and chemical recombination. This model provides important insights to further interpret the experimental results conducted with the Devanathan-Stachurski cell.