Passive properties of lean duplex stainless steels after long-term ageing in air studied using EBSD, AES, XPS and local electrochemical impedance spectroscopy

摘要

Passivity of duplex stainless steel was studied after long-term ageing in air using local electrochemical impedance spectroscopy, AES, XPS and EBSD. After mechanical polishing, the passive film was homogeneous and had a capacitive behaviour described by the CPE. After long-term ageing, a small thickening was detected and O~(2-)/OH~- was significantly higher in the austenite than in the ferrite. Austenite behaved as a blocking electrode whereas two capacitive loops were observed in the ferrite (low value of O~(2-)/OH). The loop at high frequencies was related with the oxygen reduction and the loop at low frequencies was connected with the passive film.