Silver boiler piping ID?

[Mike Lamb]

The main runs of this boiler piping is silver. What material is this???

[Bill Kibbel]

Occasionally, I'll see stainless steel piping.

[Rob Amaral]

Another reason to bring magnet..

[Mike Lamb]

I thought of grabbing my magnet but my tool box was at the other end of the crawlspace, and I was too lazy to go get it.

[CNewhouse]

Can stainless steel piping be sweated to copper fittings without galvanic corrosion?

[Marc]

The potentials between copper and stainless is about half that between copper and iron. Still, what I've seen on the net discourages such direct connections. What interesting is that the copper erodes when joined to stainless. When joined to iron, the iron is the one that erodes.

[Chad Fabry]

Stainless and copper can be sweat connected. I've seen it done with boiler systems- usually the boiler systems of engineers who worked at Kodak when Kodak was famous for being the stainless hardware supplier to felonious employees. 

I've never seen any sign of galvanic corrosion though- the 98:2 tin/copper solder likely isolates the dissimilar metals with an atoms-thick loving layer of protection.  

[Mike Lamb]

This boiler piping is about 20 yrs old. Never seen it before.