"Lloyd E. Sponenburgh" lloydspinsidemindspring.com wrote in message
. 3.70...
"Ed Huntress" fired this volley in
:

Note the comments about applying a primer within two hours. That's
something to watch for, but my recollection is that it's only relevant
to very high-performance applications. It may have something to do
with the hygroscopic property of anodizing. The chemistry of this is
over my head, but anodizing of many types, maybe all types, chemically
absorbs and binds water. It's hard to imagine that your bonding job is
going to be very sensitive to this, because the cogging bond is
probably all you need.


A freshly anodized surface forms the essence of a molecular sieve. There
are tiny, wormhole-like tunnels all through the surface of the oxide
layer. Those that are sized appropriately will entrap water molecules.

It's not exactly hygroscopic in the sense of attracting moisture by
adding to water of crystalization or by dissolution (like salt or sugar
in humid air), but any moisture that arrives is captured mechanically, so
it amounts to the same thing at a practical level.

LLoyd

Aha. Thanks, Lloyd.

--
Ed Huntress