Using in situ AFM to investigate corrosion and passivation of duplex stainless steels

This paper reports in situ atomic force microscopy (AFM) and SEM studies of the corrosion of duplex stainless steels. The results showed selective dissolution of the duplex structure, with one rapidly dissolving phase and one slowly dissolving phase. Electron probe microanalysis (EPMA) measurements showed that the weak phase contained more Cr and Mo and the resistance phase contained more Ni, which was used to assign these phases to ferrite and austenite, respectively. Copper deposition experiments showed that the resistant phase was more noble and acted as the cathode. The mode of dissolution was apparently modified after polarization of the steel in the passive range.