Liquid-Phase Ion Gun for Local Acidification of Na2S Aqueous Solution and Local Sulfidation of Fe-Cr Alloy Surface

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 Na2S 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 H2S-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 H2S generated but also to evaluate sulfidation of a material surface quantitatively.