Let me add a little more data to this for you. First, it is a Telrex antenna
and that
means it is OLD so it has had quite a lot of time to deteriorate. Personally,
I would
like my antennas to outlast me, if possible. Anyway, I acquired this antenna
when I was
living in New Hampshire and it spent most of its life near the coast in
Massachusetts so
the fact that it is located now near Portland, Oregon, 100 miles inland has
little to do
with its past life in MA where the deterioration has mostly occurred. I am
taking this
tower and antenna down anyway and not just to illustrate a badly corroded boom
to mast
plate. It will be convenient to take a picture of it when it gets on the
ground and
post it on my web page. Incidentally, other than siezing or simply breaking or
being
too expensive, I have not seen a problem with stainless hardware itself. If
you look at
a table of galvanic action, you will see that zinc is right next to aluminum in
the
series which mean less potential difference between those two metals than when
iron (the
main ingredient of all steels) is next to aluminum. Iron is considerably
farther away
from aluminum than zinc in the series and therefore has a larger potential for
galvanic
action. Another consideration is that one of the two metals involved in
galvanic action
will be the "anode" and the other the "cathode". The metal acting as the
cathode is
"sacrificed" as the galvanic action takes place. The stainless steel hardware
I have
had experience with has come through just fine (other than sometimes seizing
and/or
breaking) but not so with the aluminum it has been in contact with. What, if
any,
galvanic action takes place will be greatly affected by the environment it is
in with
one of the worst being salt water.
I don't know what grade of aluminum Telrex used for their boom to mast plates
so I can't
comment on that.
The point about sailboat spars is a very good one. I suspect the surface of the
aluminum masts and spars on sailboats have been anodized and I suspect this
would make
them much less susceptable to corrosion. I have never heard of any beam booms
or
elements being anodized . . . How about a comment or two from a sailboater?
Stan
w7ni@easystreet.com
David J. Windisch wrote:
> SNIP
> It is the environment
> that causes the problem. Fortunately I have not experienced the problem to
> the extent Stan has, and that is probably due to my being inland ~ 2.5
> miles and about 300feet above sea-level.
> 73 Earl VE7IN
> >>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>
>
> Hi, Earl and all others concerned:
>
> Hmmmmmm .. lotsa fiberglas-hulled boats with aluminum masts, booms, spars,
> and s/s rigging out there on salt water .. there has to be at least one
> reader who could comment on what these folks do to minimize or avoid the
> problems re al-s/s contact.
>
> If Stan's place is near Portland, it could be as many as 50 mi. inland, far
> enough, I would think, to avoid the salt rain on the coast.
>
> Wonder if the grade of al has anything to do with it? The antennas I've
> made have been 6061-T6 cuz 'everybody uses that' ;o).
>
> 73, Dave, K3BHJ
>
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