I have an old steam system that was converted to a 2 pipe hydronic system at some point in it's past. I'm gradually restoring the radiators in each room of the house, and as I do, I'm replacing some of the piping that is present. Mostly back to the shut-off valve in the room.
Is there any harm with using galvanized steel pipe over the black steel pipe? What I removed wasn't in too bad of order, but moving forward I'd like to replace and ensure that the joints are sealed up tight. Is there any damage that can occur to the boiler or pump by having the presence of the zinc from the galvanized coating?
I know that the black pipe has worked great in the past for Hydronic systems, but is there any reason why galvanized was not used?
I think you'll be okay (see what the pros have to say). The reason black pipe can work in a hydronic system is it is typically closed, so once any free oxygen in that loop is used up (creates rust), there isn't any more to attack the pipe. Galvanized doesn't rust in the same manner (except where the coating is cut or defective), but costs more, which is probably the reason it was not used.
Important note - I'm not a pro
Retired Defense Industry Engineer; Schluter 2.5-day Workshop Completed 2013