> beautiful aluminum armature with a nice matt patina finish after a run
through a dish washer

You have an aluminum part coated with a microscopic layer of aluminum oxide.
This gives you less protection than you'd think, as the aluminum oxide can
be scratched off fairly easily, leaving the bare aluminum.  The aluminum
oxide itself is very hard, but the aluminum is relatively soft, so you could
get some tasty aluminum oxide bits in your honey as a result of all the
scraping when frames go in and out of the extractor.  The easy scenario is
the not-quite countersunk brad in the frame that scrapes the aluminum.

The odds of damage to the aluminum would be minuscule.  Bare aluminum can be
"pitted" as a result of long-term contact with honey, but you'd have to
leave the honey in contact with the aluminum for a good long time to get any
visible "pitting".  Honey pH runs from 3.4 to 6, not very acidic.  

> safety of leaving the aluminum bare or if we should paint it with a food
grade paint to seal it.  

For food safety that is better than painting, I'd get the part anodized. Ask
your local machine shop, they should be able to suggest someone.  The acid
and electricity used in anodizing will give it a very thick layer of
aluminum oxide - the more oxide you have on the surface, the more
scratch-resistant it is.  Ask them to anodize it as if it were a boat deck
fitting - "crank it up to 11".  Anodized aluminum will perform far better
than galvanized, as honey could eat through the zinc plating that made the
sheet metal galvanized.

That said, aluminum oxide paint is a one of the best ways to avoid corrosion
on metal that will not come into contact with food.  

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