Sender: <marv@lancaironline.net> (Marvin Kaye)
To: lml
Date: Thu, 19 Dec 2002 13:00:28 -0500
Message-ID: <redirect-1930863@logan.com>
From: "Ted Stanley" <ted@vineyard.net>
Subject: Re: Piano hinge for cowlings- Hysol only? - grit blast vs. etching
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John -

Thanks for your kind comments. With respect to grit blasting vs. etching
prior to bonding it's not quite that simple.  In the previously mentioned
book on adhesives, the chapter on surface preparations is just over 50
pages.

Basically the type of surface prep is going to be a function of the type
substrates to be bonded and the type of adhesive being used. In general,
make your bond as soon as possible after the surface prep. Ensure that
everything is CLEAN. Check the surface prior to bonding by using deionized
water to ensure you have a "break free" surface (water should sheet out not
bead).

Personally I use Alumiprep 33 on aluminum prior to bonding and have had good
luck. Things I bonded 10 years ago are still stuck. Grit blasting seems OK
to me with the exception of the fact that the grit may impart impurities to
the very surface you're trying to clean. The importance of keeping the time
short between prep and bonding should not be discounted. Some active
materials such as aluminum can form oxide layers in a very short time.

With respect to the heat issue most adhesives don't take the heat very well.
There are those that do, but typically as temperature resistance improves,
adhesive quality (peel in particular) decreases. For hinges I'd go with
bonding and mechanical fasteners. The bonding makes a good "bed" thus
ensuring (or nearly so) that the hinge and won't fret. Mechanical fasteners
(rivets) addresses the peel issue. Belt and suspenders as it were.

Ted Stanley