Corrosion behaviour of ferrite and austenite phases on super duplex stainless steel in a modified green-death solution

Corrosion behaviour of super duplex stainless steel (SDSS) in acidic chloride solution was investigated electrochemically. Potentiostatic polarisations of SDSS at −0.377 and −0.447 VSHE resulted in selective dissolution of γ- and α-phases, respectively, and were utilized for fabricating single-phase electrodes. Potentiodynamic polarisation curve of SDSS could be calculated from those of single-phase electrodes. The higher corrosion current density and less noble corrosion potential of α-phase characterised by galvanic connection with γ-phase indicated that α- and γ-phases were functioned as the anode and the cathode, respectively, in the corrosion of SDSS.