Micro-electrochemical insights into pit initiation site on aged UNS S32750 super duplex stainless steel

Abstract An aging treatment of UNS S32750 super duplex stainless steel at 1173 K for 1.0 ks produced σ and secondary austenite (γ 2 ) phases in the α γ phase boundary regions. Small amount Mn-Cr oxide MnS complex inclusions were present steel. No pitting was observed during potentiodynamic polarization a small area (200 × 200 µm) without 1 M MgCl 348 K. Because electrode included α, γ, σ, phases, these their boundaries alone could not act as initiation sites pitting. The size gradually reduced from 3 mm to mm, corrosion occur region that appeared be near phase.