Inhibitory effect of La3+ on hydrogen damage of 27CrMo44S/1 steel in H2S-containing acidic solution

The effect of La3+ on the hydrogen permeation behavior of 27CrMo44S/1 steel in acidic environments containing H2S is investigated through the measurement of steady-state permeation current density (i∞), hydrogen diffusivity (D), and subsurface hydrogen concentration (C0). Results indicate that the addition of La3+ can remarkably reduce i∞. The corrosion products with La3+ involved in the film formation process in the H2S-free environment have a good hydrogen barrier effect, but the addition of La3+ almost decreases the D value of the steel in the H2S-containing environment. However, the presence of La3+ substantially reduces the C0 of the material regardless of the presence of H2S in the solution. Static immersion and tensile experiments illustrate that the addition of La3+ can improve the corrosion behavior and plasticity loss of the material in the H2S environment.