Corrosion and Hydrogenation of 17G1S-U Steel in Hydrogen-Sulfide Media of Different Concentrations

We study corrosion, hydrogenation, and mechanical properties of 17G1S-U steel in chloride-acetate solutions with hydrogen-sulfide concentrations of 25, 100, 500, and 1500 mg/dm³. For ${C}_{{\mathrm{H}}_2\mathrm{S}}$ = 25 and 100 mg/dm³, steel corrodes for 720 h with a rate of about 0.5 g/(m²·h). In these solutions, the yield limit and ultimate strength undergo insignificant changes but the relative narrowing undergoes six- and tenfold changes, respectively. Under stresses equal to 0.8σ_0.2, steel does not suffer cracking in a solution with ${C}_{{\mathrm{H}}_2\mathrm{S}}$ = 100 mg/dm³. It is shown that the corrosion of steel at ${C}_{{\mathrm{H}}_2\mathrm{S}}$ ≥ 500 mg/dm³ is accompanied by the formation of surface hydrogen-induced cracks, and the degree of hydrogenation is almost twice larger than at lower concentrations. This is a condition required for the development of hydrogen-sulfide corrosion cracking. Static and asymmetric loads on the level of threshold values in the NACE solution intensify the process of hydrogenation of steel in solutions with ${C}_{{\mathrm{H}}_2\mathrm{S}}$ = 100–1500 mg/dm³, which becomes almost identical ${C}_{{\mathrm{H}}_{\Sigma}}$ = 12.5–14.8 ppm. By analyzing various trends in the development of steel corrosion in solutions with ${C}_{{\mathrm{H}}_2\mathrm{S}}$ = 100 and 1500 mg/dm³, we conclude that the fracture of steel in these solutions is affected not only by the degree of hydrogenation of the metal but also by the nature of sulfides formed on the surface and their protective properties.