Epoxy to aluminum RIB floor?

[Paul L]

I'm trying to fasten a painted wood platform to the aluminum floor of my RIB. Its about 2ft sq. It is cut so it fits nicely on 1.5in wide flat sections on the floor. I've expoxied it twice now. The 2nd time being careful to have a clean shiny surface to attach to. The platform breaks off after a week or two use with the epoxy attached to the wood and cleanly detached from the AL. I used West expoxy with an adhesive filler.
In another thread I saw Evans recommend Click Bond. It sounds like just the right stuff, but it is a Class 3 flammable adhesive and can't be brought onto an aircraft.
Any suggestions?

[Woodland Hills]

You want a clean rough surface for the epoxy to bond to. All the aluminum oxide needs to be removed with a scotchbrite pad or similar and the surface then needs to be degreased with a solvent that leaves no residue like trichloroethane (dangerous) or starting fluid: ether (also dangerous in enclosed spaces) or pure alcohol. Make sure that any rags you use for cleanup are new or clean and don't use paper towels that bleed blue dye.

You will probably have better luck with a two part adhesive, as opposed to a laminating resin.

[model 10]

You don't want "clean and shiney". Not much sticks to clean and shiney AL. Rough it up & etch it also. You might be better off with something with more flex like E6000

[Cheechako]

I guess the Clik Bond is the iso glue like stuff (only thick) ? That's what you want if it is. They tried to sell it to us at the aluminum boat shop to use in lieu of welding stringers etc. So we tested it by gluing aluminum angle to plate. We couldn't beat it apart with a sledgehammer.

[Dan_K]

As an engineer working in a laboratory testing adhesive bonds, we found the only way to get a structural adhesive bond with aluminum is to phosphoric acid anodize the aluminum. This is an industrial process as far as I know (so not an option). To get a bond that might hold and as stated earlier, a rough surface will be needed. You might consider then prepping the surface with Alodine, as is done for prepping for painting aluminum. Alodine makes a good chemical bond with aluminum, but the bond strength will not be structural. Choosing an adhesive with the needed flexibility will be important, most epoxies will be too brittle to accommodate the expansion differences between the aluminum and the wood.

[a64pilot]

On aircraft we bond aluminum vortex generators to the aluminum wing with Loctite depend adhesive, pretty strong bond, but it's not wood though

[keepondancin]

Maybe contact West Systems and inquire about their G-Flex epoxy. There web site claims structural bond to metal. They have good tech info and support.

[Cheechako]

Well..... if 3m 5200 is as tenacious as CF members say it is just use that.... :>)

[Cadence]

Originally Posted by Paul L

I'm trying to fasten a painted wood platform to the aluminum floor of my RIB. Its about 2ft sq. It is cut so it fits nicely on 1.5in wide flat sections on the floor. I've expoxied it twice now. The 2nd time being careful to have a clean shiny surface to attach to. The platform breaks off after a week or two use with the epoxy attached to the wood and cleanly detached from the AL. I used West expoxy with an adhesive filler.
In another thread I saw Evans recommend Click Bond. It sounds like just the right stuff, but it is a Class 3 flammable adhesive and can't be brought onto an aircraft.
Any suggestions?

Try a cheap solution. Buy a tube of liquid nails. I've used it on aluminum 30 yrs ago and it is still holding.

[Paul L]

Since I don't have access to any exotic adhesives or primers(sitting in an out island in Fiji), I think I'll try 5200 next. It ought to have a lot more flexibility than the epoxy. I only need a few hundred pounds of holding power. I am using this platform to hold the dingy fuel and anchor.
Thanks for the comments.

[David M]

With the 5200, use the regular cure, not fast cure and give it a week to fully cure.

[coastalexplorer]

I write to describe Something that I was told in a boat building shop many years ago: Which I have not personally tried. The concept is to paste the epoxy resin onto the metal surface where the desired glue joint will be. and then while wearing disposable rubber gloves, vigorously rub the wet area with course abrasive paper. The principle being to roughen up the surface. While removing the oxidization, (which sort of becomes aggregate into the resin) Thus, the resin if applied sufficiently generously; It acts as a barrier to exclude oxygen from the metal. Make the bond and allow to cure.

The point about epoxy resin tending to be hard and brittle still holds true, So with the tendency for the bottom of a RIV to flex it is easy to imagine reasons for limited success.

[RaymondR]

A few years ago a friend put me onto a 2 part epoxy putty which is used to seal metal drainage pipes but which bonds to alloy. It's latest packaging calls it DEKS 2 Part Epoxy. It's available in the plumbing section of Bunnings here in Australia so might be available in the South Pacific.

[Bluefielder]

We are formulators for industrial epoxy and urethane coatings and adhesives. 40+ years.
I would recommend .... mechanical fasteners. Yep

[Captsteve53]

5200 mechanical properties:

Substrate psi kg/cm2
Wood(s):
Teak 502 35.3
Pine 680 47.8
Oak 549 38.6
Maple 656 46.1
Fir 700 49.2
Mahogany 564 39.7
Metal(s):
Steel 538 37.8
Stainless Steel 352 24.7
Aluminum 393 27.6
Brass 474 33.3
Bronze 252 17.7
Copper 198 13.9
Lead 107 7.5
Zinc (Galvanized) 484 34.0
Plastics/Polymers:
Fiberglass 362 25.5
Gelcoat 519 36.5
Polycarbonate 381 26.8
Acrylic 217 15.3
Nylon 175 12.3
ABS 231 16.2
Polypropylene 55 3.9
Polyethylene 48 3.4