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Re: [TowerTalk] Black on Cu

Subject: Re: [TowerTalk] Black on Cu
From: Martin AA6E <>
Date: Mon, 04 Sep 2006 01:39:50 -0400
List-post: <>
Nick Pair wrote:
> The black is copper oxide and a poor conductor. Most common form of copper 
> degradation. Can form deep under insulation on coax and other insulated wire. 
> Resists soldering very well.
>   If the color on the Cu is a light to dark greenish blue you have copper 
> sulphate. A common mineral in many places and a very good chemical to get rid 
> of any mold, moss, or lichen on your roof. Also sometimes seem around Cu wire 
> near your cars battery as battery vents when they get older and internal 
> resistance rises. Not very common on antenna wired unless you live near a 
> pulp mill that still uses the sulphite process once very common in northwest.
>   Either of the products is depleting the copper in your wire. The oxide is 
> generally removed with a dilute acid and the sulphate with a dilute base.
>   FWIW   neither is detrimental to signal but both to antenna life.
>   Nick
>   WB7PEK

I expect that using acid or abrasives to clean the wire would be more 
detrimental than any oxide!  It would take away more copper.  If you're 
worried about wire degradation, there's nothing you can do except remove 
the source of the oxide - air, possibly abetted by water and air pollution.

If you want to see if it's biological, you can dip it in Chlorox bleach. 
  That will kill any mold or fungus.

73 Martin AA6E

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