Aluminum oxidation and bonding

We are making a custom heatsink. Here a thin sheetmetal fin (1100
alloy) will be bonded into a slot in 6061 AL using a special epoxy.
One question that has come up is that, apparently, bonding to either
oxidized or anodized aluminum is a bad idea. We've been told, by the
epoxy vendor, that the epoxy will bond very nicely to the oxide layer
and, eventually, separate that layer away from the aluminum fin core,
thereby causing a huge reduction in thermal conductivity. A similar
situation is said to exist with anodizing.
I wonder if anyone can help me understand how to go about making these
things. The key data point in my mind is to know how quickly the
various aluminum alloys anodize. We can certainly send them out for
chemical cleaning and even sand the edge to be bonded...but how much
time do you get before the oxide layer builds up to the point where
you are back to square one? Is this time variable depending on the
alloy being used?
Any ideas?
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