N2-supplemented shielding gas promoted nitrogen solid-solution in the austenite. Secondary austenite had higher Ni but lower Cr and Mo than primary austenite. Pitting corrosion preferentially occurred at secondary austenite and Cr2N. Adding N2 in shielding gas improved pitting corrosion resistance of GTAW joint. E2209T1 weld metal had very poor pitting corrosion resistance due to inclusions.