Effect of nitrogen on corrosion of duplex stainless steel weld metal

A type 329J1 duplex stainless steel was gas tungsten arc welded without filler material in an Ar-N₂ gas mixture atmosphere with the aim of changing only the nitrogen content in the weld metal. The effect of nitrogen on the microstructure and corrosion properties of the weld metal was examined. An increase in nitrogen partial pressure increased the nitrogen content of the weld metal and brought reductions in the ferrite content and the quantity of Cr₂N nitride precipitates. Three corrosion parameters, namely, critical pitting temperature (CPT), pitting potential, and corrosion rate, were measured for weld metals having different nitrogen. contents. The CPT and pitting potential increased and corrosion rate decreased with increasing nitrogen content of the weld metal. The corrosion behaviour was explained in terms of changes in microstructure and pitting index depending on the nitrogen content of the weld metal.