Investigation of micro-electrochemical activities of oxide inclusions and microphases in duplex stainless steel and the implication on pitting corrosion |
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Authors: | Yaohua Zhang Qian Hu Mingjie Dai Feng Huang Frank Y. Cheng Jing Liu |
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Affiliation: | 1. The State Key Laboratory of Refractories and Metallurgy, Wuhan University of Science and Technology, Wuhan, China;2. Department of Mechanical and Manufacturing Engineering, University of Calgary, Calgary, Alberta, Canada |
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Abstract: | In this study, the oxide inclusions contained in the 2205 duplex stainless steel were characterized, and the pitting corrosion initiated at the inclusions was statistically analyzed. The micro-electrochemical behavior was measured by a home-designed capillary microelectrode technique. Results show that three types of oxide inclusions are contained in the steel, namely, Al–Mg–O (inclusion A), Al–Si–Ca–O (inclusion B), and Al–Mg–Si–Ca–O (inclusion C) inclusions. Inclusion A possesses higher electrochemical stability than the steel substrate, and there is no corrosion pit initiated on the inclusion. Inclusions B and C are more electrochemically active than the steel, and pitting corrosion occurs on both inclusions. The α phase has higher electrochemical activity and lower corrosion resistance than the γ phase. Pitting corrosion is more likely to occur at the inclusion/α phase interface, rather than the inclusion/γ phase interface. When the inclusion is located at the α/γ interface, the pit initiation is dominated by the α phase on the coexisting dual phases. |
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Keywords: | composition phases duplex stainless steel electrochemical activity oxide inclusion pitting corrosion |
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