Influence of Dissolved Oxygen on DL-EPR Behavior of SUS329J4L Duplex Stainless Steel after Convection Cooling

Sigma phase precipitates in duplex stainless steel during slow cooling, degrading the corrosion resistance and notch toughness. The double loop electrochemical potentiokinetic reactivation (DL-EPR) method a solution of 0.5 M H2SO4 + 0.01 KSCN NaCl is known to be good for detecting sigma phase. However, influence dissolved oxygen (DO) had not been elucidated, on-site application DL-EPR carried out. In this study, SUS329J4L was continuously cooled at different time constants by convection using nitrogen, its behavior measured with DO concentrations. A cathodic current partially appeared potentials nobler than potential due reduction oxygen. Elimination suppressed reaction, resulting adequate sensitivity detection precipitated almost same as that laboratory samples 700 mL/cm2 simulated small structures exposed 20 solution, high immersion test.