Re: ATM Aluminum solder

[Gerald Pearson & Sue Sarlette <suegerry@muscanet.com>]

My $0.02 about getting the best possible bond between metal and epoxy:

I attended the composite construction workshop at Astrofest '97.  The
guy leading the workshop said that slow metal oxidation over months or
years was the main reason for epoxy/aluminum bond failure.  For aircraft
construction, they use some metal treatment for the aluminum.  Short of
that, he recommended the method which I've used myself for many years.  


1.  Clean the surface, sand it down to bright metal, and THEN SAND THE
SURFACE SOME MORE USING SANDPAPER WET WITH FRESHLY MIXED EPOXY.  The
liquid uncured epoxy which is wetting the metal prevents any possible
contamination of the freshly-exposed metal surface.  Then mix up a fresh
batch of epoxy, wipe the dirty epoxy off of the metal surface with a
paper towel (leaving a very thin film), and proceed with whatever gluing
or fiberglassing you want to do.

2.  I use the coarsest sandpaper possible.  In my experience, the
rougher the clean metal surface is, the stronger the bond will be.

3.  Use slow setting epoxy whenever possible.  Quick setting epoxy glues
are noticably weaker.  


These ideas work on any structural metal I've tried -- aluminum, steel,
brass, copper, bronze.


        -- Gerry