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On 6 Apr 2006 08:28:01 -0700, "larry" <larry.a.schurr@boeing.com>
wrote:
>>Can you explain what you mean by Clad coating?
>
>Well... Aluminum is a whitish-gray material, not slick and shiny like
>the sheet metal you buy.
OK
>The sheetmetal product, and much plate stock,
> is almost always 'clad-coated' and to my knowledge, not available any
>other way.
Eh?
Clad coated?
Got a source for that info?
>That shiny stuff is the 'clad' which is simply more
>aluminum that has been pressed tightly to eliminate natural porosity.
>Of course, the *process* has changed over the years but the result is
>the same: shiny and slick sheetmetal.
This makes absolutely NO SENSE
>Beneath the clad coating is "raw" aluminum. This has been the bugaboo
>of corrosion problems among many. Raw aluminum is quite reactive to
>air and water and protects itself with an oxide layer of white powder
>(that also turns mysteriously black when you handle it -- kinda weird).
> Depending on alloy, once the raw surface is exposed, the oxide layer
>can go quite deep -- often deeper than the sheetstock IS.
Deeper than the sheetstock?
Like into thin air on the back side?
>The clad
>coating, while still aluminum, keeps corrsion at bay to a much greater
>extent because it reacts far, far, slower than 'raw' aluminum. Once
>this clad is gone, all bets are off.
The protective layer IS the oxide
>Sanding or etching removes this coating pretty much every time. Once
>removed, you're gonna hafta treat that surface pretty quickly with
>aluminum specific coating (like alodine). Another poster quite rightly
>pointed out that color isn't supposed to be very 'deep'. "Well-done
>fried chicken" brown is too deep. "Light Honey" brown might be more
>appropriate. Gotta go, getting hungry alla sudden :-)
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Re: Question about Alodine 1201
