Influence of Inclusions on the Pitting Behavior of Cast Duplex Stainless Steels and Patch Weld Layers

The relationship between the corrosion resistance of cast duplex stainless steel welded joints and inclusions was investigated by metallographic characterization, electrochemical tests, in situ tests, scanning electron microscopy combined with energy dispersive x-ray spectrometry and other methods. The results showed that inclusions were the main sites for pitting corrosion initiation in cast 2205 welded joints, and the MnS portion of the composite inclusions preferentially dissolved to form micropits, which triggered pitting corrosion. In addition, the density of inclusions in the heat-affected zone (HAZ) was high and the average size of inclusions was larger, resulting in poorer pitting resistance in the HAZ. And pitting was more likely to occur and subsequently a large pit was developed which ultimately led to failure.