If this is a damp location the galv will be gone fairly fast and there will be a lot of rusting.
If it is a high chloride environment then you may get accelerated attack of the SS against the bare steel.
The system is not just the internal fluids, the external is far more important- sheltered, inland is far different from coastal or offshore where you more likely to use SS piping.
Watch out for Solid Metal Embrittlement caused by the zinc in contact with the Stainless Steel. The severity of embrittlement increases with temperature, with a sharp and significant increase in severity at the Tm (melting point) of the embrittling (zinc) agent.
Thanks Cloa
Yes, I am worried about the external environment.
If it is a place where bare steel rusts then don;t do it.
There are plastic cradles for SS pipe.
Don't do it yourself as they need to be Cl free or things may get worse.
Nobody has mentioned temperature yet. If the operating temperature of the pipe is above about 400 F, stay away from the galvanized pipe shoes.
If this is exposed uninsulated piping (i.e. not above 400 F), you're onshore, not immediately on a seacoast and not in a tropical location, chances are that your galvanized shoes/u-bolts will last a very long time and will have no detrimental effects on the stainless pipe.
The design temp is 120F and this piping is uninsulated in onshore power plant environment. I have suggested using a PTFE or some other comparable layer to avoid the contact.
