Best way to epoxy Aluminum???

[bama01]

Ok,

You'd think this wouldn't be too difficult but I'm trying to epoxy two pieces of AL together. I am cleaning the surfaces thoroughly, and applying the epoxy as directed. The bond just isn't as strong as you'd think it should be. It's a tight fit situation so I'm condidering rivets if I can't get the glue thing to work out. Any ideas why I'm having bad results with epoxy?

I'm using metal epoxy BTW.

Would roughing up the surfaces matter?


AUUGGHHH!!

 

[NickE]

yes using some low grit sandpaper will help adhesion....

What are you cleaning the surfaces with?

 

[bama01]

I have access to a sand blaster, so I'll try that on them.. Rght now I'm cleaning them with alcohol first and then good ole soap an water, and then drying of course.

 

[NickE]

Try using the alcohol last, or acetone, some soaps have a rinse agent that can remain on the surfaces.

 

[bama01]

Good idea, thanks!

 

[BillPSU]

Rough up the surface to give the surface more hook for the epoxy to attach to. If you blast the surface use steel grit as it will give scratchs in the surface to again increase the hook.

 

[MikeHalloran]

You're using metal _filled_ epoxy?

Meaning, a little bit of epoxy around a lot of metal powder?

You might get better bonds with unfilled epoxy.



Mike Halloran
NOT speaking for
DeAngelo Marine Exhaust Inc.
Ft. Lauderdale, FL, USA

 

[AlanD]

Part of the problem with getting a good epoxy bond with aluminum is that the aluminum oxidizes almost immediately which means the bond isn't as good as it could be. With sailing equipment, we used to get this problem by using wetordry abrasive paper, but instead of using water as the wetting agent, we used the epoxy.

 

[NickE]

I think AlanD has the solution.

 

[bama01]

This is nuts... The sand blasting did help I'm still not getting a super strong connection though.

It's an indoor application, and I'm developing a product for a client. It could be welded but I'm looking for quick and easy, not to mention the welding would bend a key piece that has to be straight. This would be for a mass production if things work out.

I hadn't considered oxidation especially not that quickly. Of all things to come up with this simple project, holding two pieces of Al together with epoxy. I've had better luck gluing LDPE.

 

[MikeHalloran]

The oxidation you're fighting occurs in seconds, not minutes, hours or days.

Could you describe the joint configuration, and how you are evaluating its strength?

E.g. pin and socket, mortise and tenon, two flat rigid surfaces, two flexible parts, etc..

E.g. shear, tension, cleavage, peel, etc.



Mike Halloran
NOT speaking for
DeAngelo Marine Exhaust Inc.
Ft. Lauderdale, FL, USA

 

[CoryPad]

Try a different epoxy. A simple two-part epoxy should provide a very strong bond. Try Loctite or 3M brands.

Regards,

Cory

Please see FAQ731-376 for tips on how to make the best use of Eng-Tips Fora.

 

[Tmoose]

From Devcon website -

To properly prepare a metal surface:

1) If the surface is oily or greasy, degrease it with Devcon Cleaner Blend 300.

2) Abrasive-blast the surface with 25-40 grit (or coarser) to produce a good surface

profile. If you cannot abrasive-blast the surface, use a 60 grit or coarser sandpaper to achieve a similar result.

3) Immediately coat the metal surface with Devcon FL-10 Primer to prevent it from rusting.

4) Make repairs as soon as possible after blasting the substrate to avoid oxidation



\surface prep.pdf

\FL-10 primer.pdf
This primer is recommended for both their urethane products, and under metal filled epoxies.

 

[bama01]

It's a flat surface to flat surface, about 2.5 in^2. I'm evaluating the strength super simply, I can pull the pieces apart by hand, which to me is a very weak bond for an epoxy. I'm trying a different brand of epoxy now, and should know by tomorrow evening if it's any better.


Sigh...

 

[MikeHalloran]

It might be helpful for you to identify the epoxies you have already tried for us.



Mike Halloran
NOT speaking for
DeAngelo Marine Exhaust Inc.
Ft. Lauderdale, FL, USA

 

[bama01]

Good Q. So far the only name brand has been the Super Glue Gel by Loctite. Everything else was whatever you get at the Home Depot-sorry I don't have the brand names handy.

But it's clear something else has to happen to get a good bond. Sand blasting, cleaning with soap and water then alcohol isn't enough. I'm thinking "Imoose" is on the right track with a surface treatment. There's some chemistry going on I just don't understand. Hey-I'm mechanical!

 

[bama01]

Update...

Just talked to Devcon's technical people. They didn't think any surface prep is needed, sand blast, a good alcohol wipe and maintain a .01-.02 bond thickness, which I was not doing.

 

[NickE]

"Super Glue Gel "-- not good for any "real" repairs. I've found that superglue works ok in only a few situations. Papercuts are one of them.