SV: Re: SV: Re: SV: Re: Re: [sdiy] Matrix FX BBD delay part update

[KA4HJH]

>Ian Fritz wrote:
>> At 02:37 PM 9/13/2006, karl dalen wrote:
>>>
>>> --- Seb Francis <seb at burnit.co.uk> skrev:
>>>
>>> > I assumed Electroplating is plating something using electricity.
>>> But I
>>> > could be wrong...
>>
>>
>> Yes, "plating" is the deposition of metal.
>>
>>
>
>I suppose for anodising you could say the aluminium is being plated with
>oxygen (which combines with the aluminium to form aluminium oxide) ..
>but I get your point that plating usually refers to metal coating.
>
>Seb

Actually anodizing is not a form of electroplating in the familiar sense at
all. The process is functionally similar but no plating as such takes place.

Aluminum oxide is clear (Star Trek IV was close on this but not quite). All
aluminum that's been exposed to air for a few minutes is covered with it
but since you can't see it you don't know it's there (this makes soldering
aluminum a bit tricky). Unlike metallic aluminum it's also a very hard
substance which is why it's commonly used to make grinding wheels. When
aluminum is anodized the oxide layer changes its crystalline structure to
an even denser form (called "gamma", IIRC) which produces a harder finish
(it may also grow thicker in the process--my memory is failing me here).
Also, any dye present in the electrolyte will permeate the AlO layer
becoming permanently trapped in it (I can't remember if it actually
permeates the metal or not). Being denser the gamma oxide layer is also a
better conductor of heat, which is why you see so many anodized aluminum
heatsinks. Adding the dark color improves the heat dissipation.

In the case of panels, you end up with a permanently colored finish that's
hard to scratch.

-- 

Terry Bowman, KA4HJH
"The Mac Doctor"