The effect of H2S concentration and pH on hydrogen permeation in AISI 410 stainless steel in 5% NaCl

Measurements have been made of the permeation of hydrogen atoms in AISI 410 stainless steel in 5% NaCl containing varying levels of dissolved H2S at pH values between 2.6 and 4.6. In addition two tests were conducted for H2S-saturated seawater. Hydrogen permeation currents increase with increasing H2S and decreasing pH, as expected, but the permeation transients are strongly influenced by both irreversible and reversible trapping. Calculation of a diffusion coefficient is thus not readily possible based on simple Fickian diffusion theory. A thickness-normalized flux is considered the best interim method for characterizing the charging efficiency of different environments.