and potentiostatic and potentiodynamic polarization methods The adding 2%
N2 in shielding gas facilitated primary austenite formation in GTAW weld metal (WM) and suppressed
Cr2N precipitation in GTAW weld root. In the HAZ, the banded microstructure disappeared while the
coarse ferrite grains maintained same orientation as the banded ferrite in the BM. In the WM, the ferrite
had one single orientation throughout a grain, whereas several families of austenite appeared. The
austenite both in BM and WM enriched in Ni and nitro‘gen, while Cr and Mo were concentrated in the
ferrite and thus no element showed clear dendritic distribution in the WM (ER2209 and E2209T1). In
addition, the secondary austenite had higher Ni content but lower Cr and Mo content than the primary
austenite. The N2-supplemented shielding gas promoted nitrogen solid-solution in the primary and secondary
austenite. Furthermore, the secondary austenite had relatively lower pitting resistance equivalent
number (PREN) than the ferrite and primary austenite, thereby resulting in its preferential corrosion. The
Cr2N precipitation led to relatively poor resistance to pitting corrosion in three HAZs and pure Ar shielding
GTAW weld root. The N2-supplemented shielding gas improved pitting corrosion resistance of GTAW
joint by increasing PREN of secondary austenite and suppressing Cr2N precipitation. In addition, the
FCAW WM had much poorer resistance to pitting corrosion than the GTAW WM due to many O-Ti-Si-Mn
inclusions. In the BM, since the austenite with lower PREN compared to the ferrite, the pitting corrosion
occurred at the ferrite and austenite interface or within the austenite.