Believe it or not they blast quick and clean up nicely. It's like crap gets burned on the outside but is just on the surface.

 

Good to know...now I know what sort of welder I need to find.

 

What would a magnet tell you? Stainless STEEL contains enough iron to attract a magnet.

 

I can't explain the physics of it, even though they both contain a lot of steel, 300 series stainless is very slightly magnetic, 400 series is more magnetic, but both are dramatically less magnetic than carbon steel. You can easily tell if a part is made from stainless steel using a magnet.

 

No input on the cut, revers and weld?

 

If you have ever had a set out believe me I only want to do it once.
That method would be IMO better than swelling the pipe up though.

 

Cheap fix for the short term.

Fel-Pro 8194 Up-pipe Gasket Set

 

My thinking would be to find a suitable donor beforehand...I presume they would be cheap and easy to come by?

Is it one side or both that are susceptible to this pitting issue?

This could also be an niche business if someone had a TIG welder, a way to provide backing on the inside surface of the weld and a spare set of up pipes to repair, ship and charge a deposit for.

 

Bellowed up pipes fix the issue permanently. Otherwise it's just a bandaid on a shotgun blast