Constituent phases of the passive film formed on 2205 stainless steel by dynamic electrochemical impedance spectroscopy

Xue-qun Cheng1,2),Cheng-tao Li1),Chao-fang Dong1,2),and Xiao-gang Li1,2) 1) Corrosion and Protection Center,University of Science and Technology Beijing,Beijing 100083,China 2) Key Laboratory of the Ministry of Education of China for Corrosion and Protection,Beijing 100083,China

摘 要：The passive film formed on 2205 duplex stainless steel（DSS） in 0.5 M NaHCO3+0.5 M NaCl aqueous solution was characterized by electrochemical measurements,including potentiodynamic anodic polarization and dynamic electrochemical impedance spectroscopy（DEIS）.The results demonstrate that there is a great difference between the passive film evolutions of ferrite and austenite.The impedance values of ferrite are higher than those of austenite.The impedance peaks of ferritic and austenitic phases correspond to the potential of 0.15 and 0.25 V in the low potential range and correspond to 0.8 and 0.75 V in the high potential range.The evolutions of the capacitance of both phases are reverse compared to the evolutions of impedance.The thickness variations obtained from capacitance agree well with those of impedance analysis.The results can be used to explain why pitting corrosion occurs more easily in austenite phase than in ferrite phase.

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