Initiation of Sulfide Stress Cracking Using Potentiostatic Liquid-Phase Ion Gun

A liquid-phase ion gun (LPIG) was used to create a local H2S enriched environment near Cr-containing steel surface in Na2S solutions in attempt to induce sulfide stress cracking on the specimen surface. In a 1.5 mM Na2S solution, anodic polarization of LPIG Pt microelectrode at a potential of 1.90 V vs SHE resulted in that local solution was successfully acidified to below pH 4, a pseudo-sour environment. When Cr-containing steels were potentiostatically polarized under this pseudo-sour environment by LPIG, sulfides were formed on the specimen surface depending on Cr-concentration, specimen potential, and chloride ion in solution. When LPIG was operated on Cr-containing steels subjected to tensile stress using a four-point bending tester, cracks were formed on the steel surface.

Automated summary

A liquid-phase ion gun (LPIG) was used to create a local H2S enriched environment near the surface of Cr-containing steel in Na2S solutions, aiming to induce sulfide stress cracking on the specimen surface. Acidification of the local solution below pH 4, creating a pseudo-sour environment, was achieved by anodically polarizing the LPIG Pt microelectrode at a potential of 1.90 V vs SHE in a 1.5 mM Na2S solution. Under this pseudo-sour environment, sulfides were formed on the specimen surface depending on the concentration of Cr, specimen potential, and chloride ion in solution. When subjected to tensile stress and operated with LPIG, cracks were formed on the surface of Cr-containing steels using a four-point bending tester.