In TIG welding of austenitic stainless steel nitrogen is mixed with argon shielding gas in order to control delta ferrite contents of weld metal between 5-10% by volume to prevent hot cracking and corrosion network of the delta ferrite. This research studied the effects of nitrogen on pitting corrosion of the 304 and 316L austenitic stainless steel weld metals produced by TIG pulse welding. Argon and argon with nitrogen 1-4% by volume were used as shielding gas. The polarization curves of weld metals were measured in the standard NACE and 3.5 Wt% NaCl solutions. Microstructure responsibility for pitting corrosion was also studied. Increasing nitrogen contents in argon shielding gas for TIG pulse welding of the 304 and 316L austenitic stainless steel will increase the nitrogen contents in weld metals. Increasing nitrogen contents of weld metal will shift the polarization curves measured in the standard NACE and 3.5 Wt% NaCl solutions to positive potentials. Pitting potentials increase and the passive current density decrease when nitrogen contents of weld metal increase. The NACE solution has more effects on the pitting potentials and passive current density than 3.5 Wt% NaCl solution because the NACE solution has lower pH and higher NaCl contents than 3.5 Wt% NaCl solution. Pitting corrosion of the 304 and 316L austenitic stainless steel weld metals was found at the austenite and delta ferrite interfaces and propagated to austenite phases.
