Scanning electrochemical microscopic observation of corrosion reactions on a duplex stainless steel

Aoki, So  ; Taniguchi, Tomomi*; Sakai, Junichi*

The objective of this study is to clarify the preferential dissolution mechanism of a duplex stainless steel (DSS) at its corrosion potential by means of in-situ Scanning Electrochemical Microscope observation. Probe electrode was fixed above ferritic and austenitic each phase of DSS at corrosion potential. Potential of the probe electrode was polarized toward noble direction, and probe current was measured. In a probe potential range of 0-0.70 V (SHE), anodic current due to hydrogen oxidation reaction could be detected. This anodic current was larger above austenitic phase than that above ferritic phase. In a probe potential range of 0.70-1.2 V, anodic current due to Fe oxidation reaction to Fe could be detected. This anodic current was larger above ferritic phase than that above austenitic phase. Based on these results, a preferential dissolution mechanism model of a DSS at the corrosion potential is proposed using internal polarization curves.