[TowerTalk] "anodized" aluminum

[Steve Bookout]

Dennis Schaefer wrote:
> 
> I was busy cleaning up a used KT-34A this afternoon and a friend came by.
> I was scraping off some silicone rubber that had been glopped all over the
> antenna and he cautioned about doing too much scraping.  He said it would
> remove the "anodizing" from the aluminum and it would turn black.
> 
> I wasn't sure I bought this, but this is a very smart guy.  He is not an
> antenna expert, but works at the nuke plant and is very knowledgeable (he's
> an enginneer).  I have seen aluminum elements turn dull and gray after
> time, but I figured that was just a natural chemical process related to
> weather, contamination, etc.
> 
> I have to get the silicone off in order to reassemble the antenna, and so
> far it has resisted all chemical attacks (gasoline, turpentine, etc).  That
> leaves scraping, and probably a rotary wire brush.
> 
> I never thought anything special was done to aluminum tubing and it was OK
> to scrape, polish etc.  Am I wrong?  (I remember a thread on polishing
> elements awhile ago, but I don't think this was addressed).
> 
> Dennis,  W5RZ
> 
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Hello Dennis,

On this issue, I think your friend is wrong.  ENGINEERS DO NOT KNOW
EVERYTHING, contrary to what some of them might think.  I DO know
something about the process and how it's typically used.  

Sure, it would help the corrosion issue, but it would cost more and the
manufacturers would be bragging about having it.  

And, most important, Anodizing is an electrical insulator.  

Iridite on the other hand, is conductive.  Although they may look
similar to the average person, and try to achieve the same purpose
(usually), they are different processes.

All aluminum being used in commercial antennas I know of, just has it's
typical 'mill' finish.  

I have seen some antennas made for the Gov't that were iridited ($$$),
but never anodized.

They get dull from oxidation.

73 de Steve, NJ4F



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