Aluminum and Bondo


Sr Member
Anyone know if bondo (or some other product that works better) will stick to machined aluminum? I made a slip when grinding a part and need to fix it :lol:lol. The part will painted when done so maching the metal is not really an issue, just something that will stick to it well.

If possible just post if you have a product you have tried or use and it works well. I have googled for the different products and really would like more of a testimonial of what has worked and held up well for you.
You need to upgrade to a premium body filler with a 'zinc' adhesive promoter... I recommend Evercoat as almost all their body fillers except for their bottom of the line contain their own 'ZNX-7' adhesive promoter... You will need a pro-shop to get most Everyclear products though as most 'consumer' places don't carry it... You can also check out NAPA if you have a well stocked one in your area the usually stock a premium 3M brand (usually 3M Gold QBA) that has adhesive promoters that the low end 3M Bondos don't... But even then don't expect miracles, aluminum is a very hard metal to bond to...

You can also consider using JB Weld, it sticks well to aluminum, use the normal slow set not the fast set... Give it plenty of dry time and it will sand well...

And last but not least you might consider Alumiweld, if you have a Harbor Freight in your area they actually stock it in stores... This will be the most permanent, as you are actually soldering/brazing another metal as a filler...
That Alumiweld looks pretty cool. I think I am going to grab some of that from Harbor Freight tomorrow and see what I can do with it :lol.

I will test it on a few scrap pieces to see how works.
That Alumiweld looks pretty cool. I think I am going to grab some of that from Harbor Freight tomorrow and see what I can do with it :lol.

I will test it on a few scrap pieces to see how works.

As long as you wire brush or sand right before you heat it works very well, one of those 'AS SEEN ON TV' things that actually met my expectations and then some!

BUT you need to get the part HOT with an even heat over the 'weld' area and then hold the heat for a few seconds... Remember the golden rule heat the part and use the heated part to melt the Alumiweld (aka pull the flame off for a second and touch the rod to the part if it starts to melt return the flame and continue heating the area as you fill... Don't take mistaken shortcut and attempt to use the flame to do the melting, as it will melt the rod in no time flat, but it won't bond properly or at all to the piece...

I was very skeptical of the stuff at first, but my first step test was to take two sections of 1/8" aluminum flat stock and make a 'T' with a bead on each side of the joint... I then let it cool slowly as instructed, took a hammer and whacked the part flat and to my surprise the braze didn't fail... Totally blew my mind...

And on one last note, aluminum doesn't much indication of the shift from solid to liquid so if you are using a HOT torch like an OXY/ACT rig be very careful or you will end up with a blob ;)
I've used Harbor Freight's Alumiweld a few times before, and it's pretty neat stuff. I first saw the same product or something similar demonstrated at the Oshkosh air show, and car shows years ago. They patched up aluminum pop cans easily, and had other aluminum pieces to show what could be fixed: radiators, sheet aluminum, all sorts of things. I've got a few more plans for the stuff, but I just haven't gotten around to doing anything more with it yet. But count me a fan.
Aves will stick to aluminum, I don't know about long term though. I'd try Lab Metal. I used some on my Endor rifle build and it seems to have no problem sticking to aluminum.
Because of the part and the the shape that I had to follow I ended up using JB Weld to sort of fill an area and to try to reshape it (we will see once I try to machine the part straight again is it works). I picked up some of the alumiweld rods at harbor freight today and plan on playing with them this weekend. I am pretty sure they can solve another problem I have been working on for a while.

Thanks for all of the tips. I trashed a fairly expensive part and at this point I think I am going to be able to fix it.

Hmmm, that lab metal looks like some interesting stuff. I may need to pick some of that up too. :)
Last time I bought some Bondo glazing putty at Wally World they had some Bondo Plastic Metal. I bought some, but have not tried it yet.


They also make a metal fill which has aluminum flake in it so I would think it would adhere to aluminum and can be sanded to mimic metal surfaces.

From 3M:

Dynatron® Metal-Fill™ is a specialty filler that is formulated with metallic aluminum flakes to produce a metal-like finished appearance with rust-proof and water-resistant characteristics.
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