The best from a corrosion and abrasion resistance point of view is hard
anodising. That will however reduce the fatigue strength by about 50% (and I
must confess I'm not too sure what that means.) The book then goes on to state
that fatigue strength is restored by either hot water or dichromate sealing.
This is how most big aircraft parts are treated.
The really useful thing about anodising though, is that it makes epoxy and paint
stick properly. You cannot bond to aluminium without some form of etching no
matter how hard you scuff sand it. You might if you did it under vacuum although
I wouldn't be sure even then. Without etching or anodising the bond will let go
in a few years quietly and gradually as corrosion seeps in from any exposed
edge.
BTW I didn't get to read "John Bean's missive" my machine had another accursed
GPF fault "caused by CSNav" or so it claimed. It lost about 30 postings. I'm fed
up with Windoze. I curse Apple for making the classic Betamax mistake and not
licensing Mac.
Graham
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