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Primer on epoxy filler for aluminum wings before topcoats?

Posted: Thursday, July 10, 2014 7:56 AM Quote
Hi all,
I am refinishing my glider wings and thinking of using epoxy / microballoon filler to
rebuild the  wing airfoil contour. The aluminum surface was stripped clean, scrubbed with
scotch brite (the brown kind for metal) . My plan is to start filling WITHOUT etching and alodining given the
epoxy used in the filler is corrosive protective. The aluminum surface looked well abraded after the scrub.

The next step would be using a sandable epoxy primer followed by topcoats.

I wonder if this is an acceptable approach, since there have been discussion about the need to alodine the aluminum surface to protect the aluminum surface. Questions:
-Is alodine a must if the filler is corrosive protective?
-Do I really need this primer since the top coat adhesion to epoxy also known to be excellent. Spraying topcoat on epoxy primer would simplify the project and save $.

The old paint peeled off at the green chromate primer layer which makes me think the adhesion was not that great after many years exposing to the weather.

Thanks in advance
Posted: Saturday, July 12, 2014 12:08 PM Quote
If when removing finishes from aluminum and you find your self removing any corrosion as well it's always recommended to etch and alodine before priming.  If there was no corrosion you can etch and prime.  It's extremely important that regardless of which way you go the bare aluminum surface is clean. Test the surface by wiping with a white cotton towel and some thinner.  If you get a lot of black on the towel you don't have a clean surface.  We suggest pressure washing to remove all residue from the sanding/etching process.

regarding application of a filler epoxy onto bare metal I would review the manufactures instructions regarding surface prep first. If they suggest priming before filling that's what I would do.  If it says to apply to clean bare aluminum then that's what I'd do.

FYI - the majority of epoxy filler type materials do not have the anti corrosion protection in them that an epoxy primer will.  There is a difference between epoxy paints, fillers, and glues