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Re: [TowerTalk] Al-to-Al

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


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
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