Epoxy wood to aluminum? Mild emergancy here....

[JMAC]

...I've made a sign for the new Center for Maine Craft that's opening in the new travel plaza in Gardiner. I'm installing it tomorrow. It's an interior sign that lives over the double door entry to the Center. I was planning on screwing the sign directly to the entryway's anodized aluminum frame, but now the director says no to that and suggested gluing blocks to the frame to screw into. It's a 2' x 6' sign made of veneered 3/4" MDF. What kind of bond would I get with West 5 minute, or West thickened 105? Yeah, and can you respond quickly, I'll be leaving around 8:00 AM...I know, I know....

[Thorne]

Can you make wooden blocks that will hook over the edge of this frame, so that if the glue fails the sign won't kill anyone?

If the metal frame has 90 degree corners, you could make wooden blocks that would have a recess / groove to make them attach to the outsides of the corners as well as to the faces of same. That would give you some inward pressure resistance, so that all the force isn't against the glue on the face of the frame. Is there any shock associated with the frame -- slamming doors or the like?

I'm not explaining this well, but you may be able to figure it out anyway...

;0 )

[Gary E]

now the director says no screws
While the glue is drying, you might ask that guy how much insurance the "center" has to cover the sign falling on someone's head someday...

And ohh.. YOU print up a release of liability and get it signed by him

[Todd D]

In theory epoxy will bond wood to aluminum. You will get a much better bond if you rough the aluminum up with some 36 grit paper. I would also glue long strips of wood to the alumimum to get the maximum bonding surface you can. That will decrease the per square inch loading of the bond. As mentioned above, get a signed release of liability. Perhaps even demand that the center sign a statement from you acknowledging that you are not happy with the way they required you to mount the sign.

[john l]

better give that epoxy 24 hours to cure!

[TimH]

I agree that if you grind a rough surface on the aluminum you should be able to get a strong mechanical bond between the wood and aluminum

[Todd Bradshaw]

Yes but........aluminum will start to oxidize almost immediately after you sand it and the more it does, the less strength your bond will have. You want to give it the final pass with the paper just seconds before you apply the epoxy (or even "wet-sand" it right before the big glue-up using epoxy as the wet part).

In general though, this is a pretty impractical application considering that a couple of simple fasteners would do a much better and more predictable job.

[TimH]

5200 would hold without sanding.

[George Roberts]

The typical epoxy/aluminum bond strength for this type of work is zero.

Yes, there are procedures that one could follow that would produce a bond but the requirements are more substantial than wet sanding with epoxy.

Without a proper acid etch and proper primer moisture will work between the aluminum and epoxy and the sign will fall off.

[JMAC]

I'm very much interested in the sign NOT falling off. The director just responded to my email verifying that the best course of action may well be to drill away and apologize later....however I think the Maine Transit Authority is concerned about the entryway's warranty being voided if there are holes drilled and glass should break. There is framing above the entryway that I will look at tomorrow for possible points of attachment, but the sign needs to go where it was designed to go.

[Woxbox]

Second vote for 5200. It will work.

[StevenBauer]

West System makes an aluminum etching kit. Product #860 Two Part Aluminum Etch Kit


http://www.westsystem.com/webpages/images/productguide/etch.jpg



860 Aluminum Etch Kit
A two-part treatment for preparation of aluminum surfaces for bonding with epoxy. Our research shows adhesion to aluminum is significantly improved with this process. Also improves paint adhesion.
860-8 Two 1/4 pint bottles (treats about 50 sq. ft.)
860 Two 1-pint bottles (treats about 200 sq. ft.).

Maybe use g/flex epoxy, too.

http://www.westsystem.com/webpages/productinfo/guide/gflex_group.jpg

650-8 G/flex® Epoxy
A toughened, versatile, liquid epoxy for permanent waterproof bonding of fiberglass, ceramics, metals, plastics, damp and difficult-to-bond woods. With a modulus of elasticity of 150,000 PSI, it is a bit more flexible than standard epoxies and polyester, but much stiffer than adhesive sealants. This gives G/flex the ability to make structural bonds that can absorb the stress of expansion, contraction, shock and vibration. It is ideal for bonding dissimilar materials. It can be modified with West System fillers and additives, and used to wet-out fiberglass tapes and fabrics. Mixed at a 1:1 ratio, G/flex gives you 45 minutes of working time at room temperature. It reaches an initial cure in 7 to 10 hrs and full cure in 24 hrs. Click for more information (http://www.gougeonbrothers.com/G-flex). (8 fl. oz. / 236 mL)




Steven

[Todd Bradshaw]

Gougeon tests on various metal bond strengths

http://www.epoxyworks.com/22/pdf/Ew22_Effects.pdf

[JMAC]

Well that chart was interesting, I didn't know that cast iron has better holding power than other metals. Where do you think wood would be on that chart? Time to load up the van with more tools and wood and fasteners than I would like, trying to be ready for anything....

[AndreasJordahlRhude]

Can the sign be hung? from the ceiling?

[JMAC]

It may be possible to hang from the ceiling. It takes over an hour to get to the site, I hope I can find a good solution down there today.

[George Roberts]

Todd Bradshaw ---

The charts you post indicates that the strength of an epoxy/aluminum bond just sanding is 1100 pounds.

That may be true for a 2 week old bond - where the epoxy has fully cured.

It is not true for longer terms.

In general, water migrates along the interface and oxidizes the aluminum weakening the bond until the bond strength falls to zero.

Since there is no claim of test length, it is not clear that the west 860 materials are an improvement.

[pipefitter]

3M's double sided foam tape would hold better and longer than would epoxy on anodized. With age, you would be doing good to be able to remove it at all without strong solvents. It is made for mounting mirrors and plaques. Anyone that has ever tried to get it off of anything, could vouch for it's bond.

[Todd Bradshaw]

It's not my test George, I just posted it. Feel free to post your own test results or those of others which support your claims at any time. I would certainly like to see some real evidence of water migrating between the epoxy and the aluminum if you actually have any.

[TimH]

George is an expert at hanging things.

[JMAC]

Marden's saved the day. I stopped there (it's a surplus salvage store) and got some 1/16" SS wire cable. I ended up hanging the sign off a wooden cleat that I screwed to the wall above the suspended ceiling using the cable with swaged eyes that went through frame hanging brackets. This worked out well. I weighed the sign this morning-53 pounds.