Why does the back side of a GTAW root pass in stainless steel pipe corrode (or sugar) so badly if I don't have the pipe purged with argon, while the amount of corrosion on a carbon steel root pass welded without a purge seems to be minimal.
I think the chromium and nickel form this oxide. There is very little chromium by comparison in carbon steel. Not a very technical answer but Its a start.
Forum
