In situ study of selective dissolution of duplex stainless steel 2205 by electrochemical scanning tunnelling microscopy

Selective dissolution of duplex stainless steel 2205 in acidic chloride sol utions was studied in situ by electrochemical scanning tunnelling microscop y (STM). In 0.05 M H2SO4 + 1 M NaCl, no appreciable active dissolution was observed by in situ STM imaging at the corrosion potential (E-corr), but at potentials higher than E-corr + 1000 mV some selective dissolution at the austenite-ferrite boundary region occurred. In 4 M H2SO4 + 1 M HCl, STM ima ges revealed active dissolution of ferrite grains at around E-corr + 50 mV. Dissolution of austenite grains started to occur at around E-corr + 150 mV , exhibiting steps of submicron scale on the edges. (C) 2001 Elsevier Scien ce Ltd. All rights reserved.