Local sulfidation of Fe-Cr alloy surfaces was attempted by using a liquid-phase ion gun (LPIG), in which a platinum microelectrode was anodically polarized in the vicinity of the alloy surface in 0.1 M Na 2 S aqueous solution. An increase in H + -concentration, namely local acidification, of the solution in the narrow space between the microelectrode and alloy surface successfully induced the formation of an H 2 S-concentrated environment and resulted in local sulfidation of the Fe-Cr alloy surface. The degree of sulfidation was dependent on acidification conditions such as the microelectrode current, specimen electrode potential and Cr concentration of the alloy. The use of an LPIG enables a sulfidation test not only to restrict the amount of H 2 S generated but also to evaluate sulfidation of a material surface quantitatively.

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.