Pitting corrosion resistance of different micro-zones in 2205 duplex stainless steel welded joints

2205 duplex stainless steel was selected as the research material. The microstructures of different micro-zones of the welded joint were characterized using optical microscopy (OM) and scanning electron microscopy (SEM), and the phase fractions were calculated. The pitting corrosion resistance of various micro-zones was evaluated through potentiodynamic polarization tests and critical pitting temperature (CPT) measurements. Furthermore, the micro-morphology after electrochemical testing was observed to investigate factors influencing pitting corrosion. The results show that the proportion of austenite at the heat-affected zone (HAZ) is the lowest, and there is a Cr₂N precipitate phase. The proportion of austenite in the weld filler layer is the highest. The proportion of austenite in the root weld layer is relatively low. The intragranular austenite (IGA) is distributed in a fine and dispersed manner, and there are many secondary austenites. For the HAZ, the precipitation of the Cr₂N phase and the lowest austenite content result in the poorest resistance to pitting corrosion. The root weld layer, affected by subsequent thermal cycles, undergoes secondary austenite precipitation, and its pitting corrosion resistance is lower than that of the filler layer and the cover layer. The base material demonstrates the best pitting corrosion resistance overall, though Mg-Al-O oxide inclusions within it can serve as initiation sites for pitting corrosion.