Its true that anodize is a non conductive hard coating on aluminum
while the alodine/iridite/etc are chromate conversion coatings which
are quite conductive. They stabilize the aluminum from the long term
effects of oxidation which increases surface resistance and besides,
it looks ugly.
Phil C. says that Henry anodizes their PA chassis and uses
lockwashers to 'dig' through the coating to the bare metal underneath.
In high power RF work, we stay away from anodizing; also many drawers
in the lab are full of brass hardware, or good nonmagnetic stainless.
Chromate Conversion coatings are, on the other hand, welcomed and
actually required for many RF systems under mil specs. No serrated
lockwashers are required, and you mount a component to the chassis,
it makes reasonable contact for RF current.
Anodizing looks really nice, forever. You can get nice colors like
green, red, black, whatever the stylists say the 'in' color is this
year to sell gadgets. I recommend that the home constructor stay away
from it for things where you have surface RF connections or current
in the skin. Use it for front panels if you must.
73
John
K5PRO
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