[Amps] Anodize versus alodine/chromate conversion

[John T. M. Lyles]

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