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 solutions was studied in situ by electrochemical scanning tunnelling microscopy (STM). In 0.05 M H 2SO 4+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 H 2SO 4+1 M HCl, STM images 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.