[TowerTalk] Al-to-Al

[john at kk9a.com]

I wrote the galvanic corrosion post, not Kirk. At my Aruba station
stainless steel ate up any aluminum that it was in contact with. After
seeing this I am always concerned about using dissimilar metals. Perhaps
the grease in the SS-30 keeps out moisture and prevents corrosion from
occurring.

John KK9A


To:	towertalk at contesting.com
Subject:	Re: [TowerTalk] Al-to-Al
From:	Patrick Greenlee <patrick_g at windstream.net>
Date:	Wed, 14 Feb 2018 08:30:13 -0600


On 2/13/2018 8:47 PM, Kirk Kleinschmidt via TowerTalk wrote:
"Not intended for use with aluminum where galvanic corrosion
could be a significant issue".

If I saw comments from the MFG telling me to not use the product where
galvanic corrosion could be significant I'd listen up.

Galvanic corrosion is another way of saying dissimilar metals corrosion.  
If   A L L   metals in contact with each other are the same then no
galvanic corrosion. I'd be leery of a powdered copper in a paste agent on
an aluminum to aluminum or aluminum to xxxx joint.

Back when the big rocks were still hot I took a sabbatical and did some
marine field service engineering.  (Commercial radiotelephone lisc with
ship's radar endorsement) I saw lots of antenna installations where coax
shields were connected to aluminum antenna mounts welded to the vessel's
aluminum superstructure. Typically a stainless steel bolt would hold a tin
coated copper terminal (ring or spade) to the aluminum antenna mount,
sometimes with silicone caulk over the connection.  Galvanic corrosion ate
big pits or made holes in the aluminum.  Improperly protected shield would
be mush or gone and sometimes the terminals were eaten or nearly so
themselves.

The longest lasting connections seemed to be with stainless bolts with
stainless flat washers on both sides of the aluminum.  The ring or spade
terminal would then only contact the stainless. Generous cover of silicone
caulk over all exposed coax shield, crimp terminals, and all of the
stainless mounting hardware.  YMMV  but this is what I saw.   Oh, some
techs painted all exposed non aluminum components in the mix with liquid
tape before covering with silicone caulk.  They used the GE 50  year
caulk, not the cheaper varieties.

Patrick        NJ5G