Scanning electrochemical microscopy detection of dissolved sulfur species from inclusions in stainless steel

The dissolution of MnS inclusions in stainless steels (SS) 303 and 304 duri ng initiation of pitting corrosion in an aqueous solution containing 10 mM KI and 0.1 M NaCl was investigated with use of a scanning electrochemical m icroscope (SECM). The dissolution products of MnS were detected amperometri cally at a carbon fiber SECM tip using I-/I-3(-) as the redox mediator. SEC M images showed that the sulfur species are slowly generated above previous ly identified MnS inclusions. The SECM tip current was stable up to 100 min , depending on the potential applied to the SS 304. SECM was found to be us eful in mapping local concentration distributions of sulfur and their evolu tion in time during dissolution. (C) 2000 The Electrochemical Society. S001 3-4651(00)02-085-1. All rights reserved.