Impact of active to inert shielding gas transition on the corrosion behavior of wire arc additively manufactured duplex stainless steel

• Investigation of microstructure and corrosion behaviour WAAMed duplex stainless steel under inert and active shielding gases. • Active shielding gas forms complex oxides, reducing surface homogeneity and passive layer stability, lowering corrosion resistance. • Residual strain analysis shows secondary and intragranular austenite worsen corrosion performance. • Electrochemical tests show WAAMed DSS under argon has 3x higher corrosion resistance than under active shielding gas. This study systematically examined the effects of inert (pure argon) and active (argon + 2 wt% oxygen) shielding gases on the corrosion behavior of wire arc additively manufactured (WAAM) duplex stainless steel (DSS), named Ar P and Ar O . Active shielding gases are commonly used in arc welding to enhance arc stability and efficiency, which prompted their selection in this study. Adding 2 % oxygen introduced ∼ 0.1 % oxygen into Ar O , with thermodynamic simulations suggesting potential spinel phase formation but microstructural analyses revealed more complex oxide inclusions in Ar O , reducing surface homogeneity and increasing intragranular and secondary austenite formation. Kernel Average Misorientation (KAM) analysis indicated higher residual strain in these areas. Electrochemical tests, including Open Circuit Potential (OCP), Electrochemical Impedance Spectroscopy (EIS), and Potentiodynamic Polarization, demonstrated superior corrosion resistance in Ar P , with higher OCP (+73 mV), corrosion potential (+39 mV), and significantly lower corrosion current density (13 μA/cm 2 vs. 49 μA/cm 2 ), leading to ∼ 3 times greater corrosion resistance. This improvement is attributed to Ar P ’s thicker, less defective passive layer (87.3 nm vs. 14.0 nm). Corroded surface morphology indicated selective dissolution of δ-ferrite phase and likely pitting around inclusions. These findings highlight that active shielding gas in WAAM deteriorates the corrosion resistance of DSS.