"Jim Wilkins" writes:

....

Thanks. I've acquired a heap of galvanized tubing that might become an
upgrade to my 50' antenna mast, and was wondering if I'd missed a
reason why welding on a structure was discouraged, since it's how
ships are built.

* you'd burn the galv away around the weld - and the weld never has
any galv (spray with zinc-based paint - which will need periodically
reapiring / re-applying)

* you are not supposed to weld over galv. Zink toxicity & disturbs
arc (arc goes a lilac colour) & could affect weld strength and
fusion