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

Abstract

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