In duplex stainless steel, the two constituent phases, namely ferritic (α) and austenitic (γ) phases, have different crystal structure and chemical composition. They may thus exhibit different corrosion resistances in aqueous environment. In this investigation, an electrochemical technique with spatial resolution was employed to measure the potential difference between these two constituent phases in 2205 duplex stainless steel. Image analyzing techniques were also used to examine the preferential corrosion between α and γ phases. The experimental results showed that ferrite had a higher potential than austenite in 0.01 M NaCl solution. In 2M H2SO4 + xM HCl solution, two distinct peaks appeared in the anodic polarization curve in the passive-to-active transition region. Preferential corrosion occurred in the ferrite phase at a lower anodic peak potential, while in austenite at a higher anodic peak potential.

Subject
Scanning electron microscopy, Constituents, Potential differences, Anode potential, Micrography, Potential measurements, Selective dissolution, Sodium chloride solution, Duplex stainless steel, Dealloying, Electrochemical potential, Austenite, Electrode potential
Keywords:
Duplex stainless steel, selective corrosion, micro-area potential distribution
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2003
Association for Materials Protection and Performance (AMPP)
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