RE: [TCML] primary tubing

["Brian" <brianv@xxxxxxxx>]

Herr Zapp,
You are correct in that they are similar however there are some differences,
aluminum is actually put into an acid bath to create the anodize and change
the molecular structure of the surface, I have tested various types of
anodizing for voltage withstand, as anodizing changes the chemical makeup of
the surface, normal is depth is anywhere from 1/16" to 1/32" below the
surface. I have sent samples of aluminum to several anodizing manufactures
to have the samples anodized so I could test the voltage withstand level,
and I have found that it will handle about 450Vac RMS before it finally
blows a hole in the anodized layer. The purpose of the test was to determine
whether or not I could use conductive ink right on the aluminum at 240Vac
without any insulation between the ink and aluminum. And the answer was yes,
however due to the depth of the anodized layer, I felt it would not pass the
UL test that was required. But the idea worked perfect, and we ended up
using it for the low voltage applications. 

One of the other factors I noticed when running this on 6018 aluminum was
the heat transfer was not uniform through out the surface of the aluminum. I
had done thermal imaging of the heat transfer of non anodized aluminum and
compared the results with anodized aluminum, and clearly heat transformation
is not uniform on anodized aluminum, however it is able withstand a lot of
heat without damage, I was able to reach 300C without any warping of the
plate, non anodized aluminum showed signs of warping at that level using the
same thickness and square inch surface area for both tests and also when
using non anodized I needed insulation between the heater and plate, I used
kapton tape and that slowed the heat transfer down. Even though the heat
transfer was not uniform the transfer was also quicker using anodized
because of the insulation I'm sure. What I was trying to do was find a more
efficient way of heating up these small plates. The conclusions of the test
was yes we could not use it, only because it would not pass the UL creepage
distance in my mind.

I have not tried any of these tests on hard anodized aluminum so I cannot
say how that performs compared to soft anodized.


--Brian

-----Original Message-----
From: Quarkster [mailto:quarkster@xxxxxxx] 
Sent: Sunday, November 08, 2009 10:21 PM
To: Tesla Coil Mailing List
Subject: Re: [TCML] primary tubing

Brian -

Actually, "anodized aluminum and "oxidized aluminum" are essentially the 
same thing, a surface film of aluminum oxide, just obtained by different 
processes.

Conventional anodizing is an electrochemical process for creating a surface 
of aluminum oxide; "hard anodizing" creates an even thicker oxide layer. 
"Oxidized aluminum" is the result of a naturally occurring process that 
occurs when a raw aluminum surface is exposed to atmospheric air.

(Anodizing leaves a surface that looks very much like raw aluminum; the 
oxide film is essentially invisible. After anodizing, a secondary dyeing 
process is frequently used to add a distinctive color to the oxide film.)

A typical anodized surface will be non-conductive when checked with a 
multimeter using blunt probes that do not penetrate through the thin oxide 
layer. A hard-anodized surface will be non-conductive even when checked with

pointed probes, at moderate pressure. The natural oxide film on a random 
piece of aluminum can vary greatly in thickness, depending on the atmosphere

that the aluminum has been exposed to, and the duration of the exposure. Any

raw aluminum surface that's been exposed to a marine environment (but not 
submerged in salt water) will usually show a very thick oxide layer.

I think the potential problem with using aluminum as a high-current 
conductor (primary coil) in a Tesla coil is not so much the material's 
resistivity, or any "skin-effect" phenomenon, but the difficulty in creating

reliable, low-resistance connections, especially at an adjustable tap-point.

Regards,
Herr Zapp


----- Original Message ----- 
From: "Brian" <brianv@xxxxxxxx>
To: "'Tesla Coil Mailing List'" <tesla@xxxxxxxxxx>
Sent: Sunday, November 08, 2009 2:50 PM
Subject: Re: [TCML] primary tubing


> Greg,
>
> What I meant was oxidization not anodization, I had anodized aluminum on 
> the
> brain for some reason, just keep this in mind, anodized = Good, Oxidized =
> bad. Oxidized aluminum will cause hi resistive connections and in turn
> create heat.  So I really did not mean anodized that was a my bad part on
> me.
>
>
>
> --Brian
>
> _______________________________________________
> Tesla mailing list
> Tesla@xxxxxxxxxx
> http://www.pupman.com/mailman/listinfo/tesla 



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