Effect of Hydrogen Sulfide on Hydrogen Entry Behavior of Low Alloy Steel

Effects of hydrogen sulfide (H2S) on behavior of hydrogen entering into low alloy steel were investigated using electrochemical hydrogen permeation technique. In this study, hydrogen entry sides were charged galvanostatically to control rate of hydrogen evolution reaction. In pH 3.0 acetic buffer solution with 0.1 MPa H2S or N-2, potential, charging current density and permeation current density were measured. Hydrogen permeation current density had a linear relation to second root of hydrogen charging current density, which means hydrogen evolution reaction proceeds under Volmer-Tafel mechanism. For analyzing the results of this study, the efficiency of hydrogen entry were calculated from the relationships among hydrogen charging current density, hydrogen permeation current density and hydrogen overpotential. It was found that the efficiency of hydrogen entry was drastically higher in H2S environment than in N-2 environment. On the other hand, the coverage of hydrogen atoms adsorbed on hydrogen entry side did not change in H2S environment. All these results suggested that, although hydrogen coverage was not changed, hydrogen entry was accelerated in H2S environment.