Pitting was observed on a 6-in. (15cm) Flare piping made of resistance welded stainless steel ASTM A312 Gr. TP 316L pipes, before going into service. The pits were in the Heat Affected Zone (HAZ) and Fusion Zone (FZ) boundary of the pipe seam welds. The seam welds were located at 6 O’clock position so that moisture had been collected on them. The FZ also was uniformly corroded. Tests indicated that the material does not sensitize during welding, but it showed a high corrosion rate in Nitric Acid test according to ASTM A242. The existence of higher number of inclusions can be responsible for the high corrosion rate. In fact large inclusions were found in the welded area which can be responsible for pitting. The general corrosion of the FZ was due to galvanic effect between inter-dendritic delta ferrite and the cored austenitic in the weld area. It was shown that the micro-structure affects the electrochemical and pitting behavior of the various regions of the weldment.