Investigation of the resistance to localized corrosion associated with microstructure of tube-to-tube sheet welds of UNS S32050 super austenitic stainless steel for seawater cooled condenser

Abstract

The behaviors of localized corrosion associated with microstructure of tube-to-tube sheet welds of UNS S32050 super austenitic stainless steel for seawater cooled condenser were investigated in highly concentrated chloride environments. In the interdendritic region, Cr and Mo as α-stabilizers were enriched and N as the γ-stabilizer was depleted whereas in the dendrite core, Cr and Mo were depleted and N was enriched. Based on the PRENIR and PRENDC values, the localized corrosion was selectively initiated at the dendrite core (DC) because the PREN value of the dendrite core was much smaller than that of the interdendritic region (IR). It was found that the resistance to localized corrosion of the UNS S32050 SASS tube-to-tube sheet welds at least as good as that of a UNS S31254 SASS base metal with PREN 47 in highly acidified chloride environments. © 2011 The Japan Institute of Metals.