Electrochemical hydrogen permeation test: An experimental review

Hydrogen permeation through metallic alloys is a physical phenomenon of interest in metallurgy. Tests aimed to measure it provide valuable information on diffusion coefficients, the nature of the surface processes related to hydrogen uptake and the presence of traps in the material. Electrochemical permeation testing methods are standardized by ISO and ASTM, a fact that contributes to its widespread use in research. These standard methods are applied in literature with a significant degree of freedom, leading to a variety of results and interpretations. Thus, when setting the testing conditions for new alloys or service environments, it is essential to distinguish which previous data and results are proper for reference in each case study. This paper reviews the richness of the testing scenarios present in literature, providing the background for decision-making on their use accompanied by experimental proof of those phenomena found in low-alloy steel permeation testing. • How hydrogen permeation model choice can bias recent research results is explained. • Test potentials/current density selection is discussed to support decision-making. • The effect of the most common variations of the testing conditions is explained. • Phenomena behind anomalous hydrogen permeation curves is revised. • A reference text is given aimed to maintain the rigor in hydrogen permeation research.