Can Electrochemical Charging Replace Hydrogen Gas Charging During Hydrogen Embrittlement Testing?

Abstract This paper presents the output from a study with the aim to correlate hydrogen gas charging and electrochemical charging for a X65 pipeline steel. The hydrogen uptake and diffusivity were evaluated via the permeation technique by employing both hydrogen gas charging and electrochemical charging. The effective diffusion coefficient, Deff, was determined by partial transients. The sub-surface hydrogen concentration, C0R, was then employed to determine the equivalent hydrogen pressure, pH2eq, of electrochemical charging conditions. In parallel, a permeation cell consisting of two membranes with thickness 6 mm welded together with a narrow gap in between was built. This unit was exposed to equal cathodic polarization conditions as the electrochemical permeation cell. The equilibrium pressure in the gap was measured and compared to the calculated hydrogen pressure from the gas permeation test with good correlation. Finally, an initial evaluation through toughness tests with the same X65 material executed in i) hydrogen gas and ii) electrolytic charging at equivalent hydrogen concentrations, gave promising results concerning the correctness of the correlation between the two hydrogen sources.