Reversible hydrogen trapping in a 3.5NiCrMoV medium strength steel

• Hydrogen permeation experiments were used to investigate reversible hydrogen trapping.
• The reversible trap density depended on the hydrogen charging potential.
• The reversible trap density was higher at a less negative potential.
• The reversible trap density at ∼−1.500 VAg/AgCl in 0.1 M NaOH was ∼1017 sites cm−3.

Reversible hydrogen trapping was investigated in a 3.5NiCrMoV quenched and tempered martensitic steel by means of hydrogen permeation experiments. The lattice diffusion coefficient was 1.29 × 10−6 cm2 s−1. Two methods ((i) Oriani–Dong model and (ii) permeation partial transients) were used for the evaluation of the reversible-trap density at various charging conditions. The results from both methods indicated that (i) there was a higher reversible-trap density at a less negative potential and (ii) the total density of (reversible) traps influencing hydrogen diffusion between −1.700 VAg/AgCl and −1.100 VAg/AgCl was in the magnitude of 1018 sites cm−3.