Downside to welding adjacent to existing weld?

[valveng]

I am investigating a through wall leak on an 8 inch pipe weld (open root weld performed in 2005). In 2005 the original circumferential weld was cut and then rewelded. the new weld is in contact with the original weld on one side and the pipe base metal on the other. The original weld has preferentially corroded (raw water system) resulting in the through wall leak. The pipe and welds are carbon steel. Is it possible for the new weld to sensitize the old weld somehow and make it more susceptible to corrosion?

 

[metengr]

valveng;
No. What is more likely is the repair weld was of a slightly different chemical composition resulting in the remnant weld becoming more anodic in behavior. Sensitization is not observed in carbon and low alloy steel.