Tom Miller wrote:
Have you checked out hot dip galvanizing? Gives a zinc coating
that protects both as a covering and as cathodic protection.

Yes, I did. The problem, as I mentioned in the original
posting, is what to do after welding the various sections
together. I'm not aware of any way to "touch up" hot dip
galvanizing in the field. Is there one? Do the various
zinc-containing paint products work well?

Of course, I am ignoring the aesthetic aspects of galvanizing.
My wife might have something to say about that. :-)

Alan