Galvanic Effect between Ferrite and Austenite in 2205 Duplex Stainless Steel

The exclusive ferritic phase (α-phase) and austenitic phase (γ-phase) specimens were prepared on duplex stainless steel (DSS) on the basis of selective dissolution method. The electrochemical behaviors of α-phase and γ-phase in 3.5% NaCl solution and 2 mol/L H2SO4+0.5 mol/L HCl solution were investigated. The results show that the open circuit potential of α-phase was lower than that of γ-phase, while the impedance of α-phase was higher. An electrochemical method, a micro-electrolytic cell arrangement and XPS testing were used for the electrochemical measurements to study the galvanic effect between two phases in DSS. It was found that α-phase contributed to the formation of passive film on γ-phase, so as to improve the corrosion resistance of the duplex stainless steel. The effect between two phases was related to the distance between them.