Abstract
Hydrogen Embrittlement can cause unexpected failures in steel structures. To have a better understanding of this phenomenon, hydrogen sorption/desorption properties need to be characterized. In an aqueous environment, hydrogen can be produced by electrochemical reduction and adsorb on the metal surface. Subsequently the adsorbed hydrogen can follow two routes: either recombination to generate hydrogen molecules in a gaseous state, or absorption followed by diffusion in the metal microstructure. Once hydrogen is incorporated, it interacts with the microstructural constituents (different phases, carbides, grain-boundaries etc.).
In the present work, an electrochemical methodology, based on cyclic voltammetry and potentiostatic polarization, was developed and elaborated on plain carbon steel. It is now used to compare H-sorption properties for different steel alloys, containing different phases and/or different ratios of phases.
The electrochemical procedure is based on first preconditioning the steel using cyclic voltammetry (CV), followed by potentiostatic cathodic hydrogen charging, and then CV to study the hydrogen desorption. All steps are consecutively performed to avoid spontaneous hydrogen loss from the steel during the procedure. This procedure allows us to gain insight in the H-saturation level of each type of steel under the potentiostatic charging condition. Complimentary H-detection methods are used to verify the steel-hydrogen interaction. In order to elucidate the H-sorption/desorption mechanism in the steel with respect to certain phases, in-depth microstructure characterization is performed. To sum up, this newly developed procedure allows the comparative assessment of the different fully characterized steel alloys, giving a valuable insight in the contribution of each specific phase in the H-sorption properties.