Please help me pick an epoxy for this application

Hey guys,

Can anyone recommend a product that I don't need to get through weird industrial back channels that would fit this criteria:

-meant to have a death-grip on aluminum

-not especially strong but flexible

-resilient to the elements (wind/sun/water)

I'm building a new splitter out of aluminum and I'm using my round over bead roller die to roll a smooth leading edge on it and I need to fill the resultant trough on top. I may just weld a plate over top but I'm leaning towards filling it bondo-like and painting the panel. So the fillet doesn't need to be structural in terms of holding metal together but it does need to keep a good grip on it while it vibrates around and maybe deflects a bit from unexpected encounters with the Earth.

Aero-Poxy lite from Aircraft Spruce is the one I would try in this application. It is an epoxy filler material, think bondo, but not polyester based. Mixed by weight, and it is bugger all difficult to mix, but it grips super well to aluminum.

No real experience but...

http://www.totalboat.com/product/flexepox-flexible-epoxy-adhesive/

I really like the loc-tite metal-specific stuff for store-bought, with the j-b weld a close second. A buddy uses normal jb weld to fill in cavaties in intake manifolds and heads for porting, and claims to have never had any issues. He does dremel grooves, but its pretty straightforward. 

Honestly even kittyhair seems enough for your application if roughed up a lil on the edges. 

Thanks guys! 

TurnerX19 said:

Aero-Poxy lite from Aircraft Spruce is the one I would try in this application. It is an epoxy filler material, think bondo, but not polyester based. Mixed by weight, and it is bugger all difficult to mix, but it grips super well to aluminum.

Cool, my local Aircraft Spruce has it, will give it a shot! Claims to be easily sandable too.

In reply to BigD :

Yes it is very sandable. I have used it enough to know that it is also pretty sensitive to mix ratio. Mix by weight. Stir both parts individually in their cans before you put them together too. Both parts separate fairly quickly in storage, but do not appear that way when you open the cans.

TurnerX19 said:

In reply to BigD :

Yes it is very sandable. I have used it enough to know that it is also pretty sensitive to mix ratio. Mix by weight. Stir both parts individually in their cans before you put them together too. Both parts separate fairly quickly in storage, but do not appear that way when you open the cans.

Thanks, yup I learned that lesson with polysulfide sealants. Now I always stir up the parts and use a food scale

This stuff was mentioned on the shop tool livestream the other day. I don't know if it would work or not.

https://www.belzona.com/en/products/1000/1111.aspx

I half wonder about using some of the glass bubble lightweight filler stuff (as in tiny hollow glass spheres as a powder you mix into your matrix of choice) for an application like that, since I think it adds sandability, and it definitely adds lightness...

just remember that most epoxies are not "sun safe" you will have to coat them with something or they will eventually get brittle and break down.

In reply to Ransom :

The Aero Poxy Light already contains micro balloons, that is how it gets bulky and light simultaniously. I have tried mixing my own, but the Aero Poxy was lighter and stronger than what I could make. Easier to finish too.

Thanks guys, I'll give the aeropoxy a shot, sounds like a good solution. I have some microballoons around to add too if it helps but in my experience it makes the epoxy stiffer.

Regarding sun safe, yep, that's why it's part of the criteria but the aero and marine stuff usually fits the bill.

The Belzona stuff looks interesting, not sure where to get it locally but the idea of steel particles mixed into an epoxy to be fused with aluminum sounds like a bad long term idea. Granted I'm no chemist so it may be a baseless concern but in my experience, steel and aluminum don't a happy marriage make.

The search continues... got some aeropoxy, cleaned up a sheet of scrap alu, scuffed it with maroon scotchbrite, cleaned it with alcohol and let the stuff cure overnight. Tried bending it at the edge of the glue to see what it would take to crack it and it separated pretty easily, and a chunked off. I don't know if I could have done more to prepare the surface but I'm also not a fan of how hard it dries. I hoped the long drying time would mean it dries more pliable as is usually the case with epoxies but this stuff is really brittle. Definitely light though... Going to give 3M a call tomorrow to see what they recommend.

https://www.amazon.com/Chemical-Plastics-All-Metal-1-Quart-USC-14060/dp/B0082LFAI6/ref=sr_1_2?keywords=aluminum+filler&qid=1571098407&s=automotive&sr=1-2 

??

It would take some research but maybe one of the cartridge type of structural adhesives might be an option? Just an example, there are quite a few options https://www.amazon.com/3M-08115-Panel-Bonding-Adhesive/dp/B000PEW4MI/ref=sr_1_3?keywords=structural+adhesive&qid=1571099584&sr=8-3

Fueled by Caffeine said:

https://www.amazon.com/Chemical-Plastics-All-Metal-1-Quart-USC-14060/dp/B0082LFAI6/ref=sr_1_2?keywords=aluminum+filler&qid=1571098407&s=automotive&sr=1-2 

 

??

Ooh that looks promising... even powdercoatable, which is something I might want to do.

I'd sand the Aluminum much more coarsely to create a better 'key' for the filler to mechanically bite to.

Then I'd try alumibrite or similar oxidation remover/mild etch.

Prep is the key here.

Without know exactly your plan, you may be able to prep the aluminum for a high quality epoxy primer, apply a few heavy coats, sand and then do the filling/shaping on top of the epoxy paint.

Here is an Aluminum etch.

https://www.aircraftspruce.com/catalog/cspages/alumcleaner.php

I found this older article I'd seen in the past about bond strength.

Sanding to 80 grit is their guideline too

https://www.epoxyworks.com/index.php/aluminum-adhesion/

Thanks! Makes sense, I'll try again with coarser grit, maybe a few patches with 30 up to 80 grit to see if even gnarlier gouges help.

Foxworx said:

Here is an Aluminum etch.

https://www.aircraftspruce.com/catalog/cspages/alumcleaner.php

Going to order some of this stuff too... I wonder if it could be a good aluminum welding prep wipe vs acetone.

Would drilling holes in the aluminium help the epoxy grip? Sort of like a plug weld. Maybe drill the holes through both pieces?

In reply to BigD :

THe Alumabrite is cheaper for cleaning. I'd suggest rinsing either product off with water before hitting it with the welder. Both products have Acids in them and might make for some undesirable vapors.

Picora makes a sealant that would work but it is not sandable but it bonds really well to aluminum and is rated for the outside exposure. 
 

I can get the specific type later at my office. 

The sanding did it, thanks guys! I have the aluminum etch coming too which I'll use.

I hit the left side with 80 grit only, and the right side with 80 followed by 40, both worked great, looks like the stuff will stay attached to the splitter even if a wall eats it

Just to land this plane, the Aeropoxy with the sanding and etch did the trick