Epoxy to Aluminium

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Has anyone here ever laminated epoxy to aluminium? I'm redoing the mast step area on my J24, the mast sits on an aluminium beam which is laminated to the bottom the hull. The old poly fiberglass around the beam was tired and I'm redoing the area with epoxy.

The pro's seem to be using Plexus but its fierce pricey. West System do a #860 etch kit, and I'm using west epoxy so that might seem like the best option, but I was wondering would sikaflex 292 (which I have) be better to bond to the aluminium first? Then laminate the epoxy over that once cured? I'm thinking to use the 205 cleaner and 206 primer for better adhesion of the sika to the alu. The alu beam has a small bit of pitting so using the sikaflex first sounds better to fair the beam first.
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Along with the appropriate choice of etch/primer, a lot of the same story that applies to lead (keel fairing) applies to the I-beam as well. Most if not all of the repair work we do to J24s is dependent on secondary mechanical bonds (at which epoxy excels), which are enhanced in metal to epoxy not only by having a properly cleaned surface, but by heavily abrading the surfaces to be bonded. Think 45 or 60 grit grinding disc, flap wheel or die in tight quarters to give the aluminum some tooth where it will be bonded. If it feel smooth and slick to the touch, that's what epoxy will experience. If it feels grippy, that's good.

Assuming you've contact your local measurer to review the scope and type of work you're doing, and that the repairs are appropriate to class rules . . .
Bonding epoxy resin to aluminum has a few tricks- all of which are mentioned by WEST product information. I simply rough up the metal , mix the epoxy, use wet sanding paper and sand the epoxy into the metal, then laminate biaxial materials to that. G flex does exceed at bonding to aluminum, and is more flexible.