I know this is an easy search, and a no-brainer to those who are experienced… but apparently copper and galvanized pipe are incompatible (which is why I have a union on my water heater).

If I’m using ENT or chain link top rail as an antenna mast I need to ground it.  To ground it I should use brass pipe clamps.  Brass contains zinc and is compatible with galvanized pipe (copper is not compatible and will chemically etch the zinc from the pipe and it will rust at that spot).

I should keep watch if I’m using a bare ground conductor that it doesn’t touch the mast either, and also verify the type of metal the mast supports are.

(www.repeater-builder.com/antenna/site-stuff/radiositerules.html)

(http://www.askcodeman.com/viewtopic.php?f=9&t=316)