Silicone used on aluminum panels

[Studebaker396]

I'm in the process of pulling the trigger on buying a Type 65 coupe. Been researching the forums trying to find out as much as I can . I'm experienced at building street rods and restoring muscle cars. What is the reason that silicone is used for the aluminum panels plus riviting instead of using epoxy or some kind of structural automotive adhesive? Thanks

[UnhipPopano]

There are at least 2 threads on this in the 818 section. The thought on this is that it works, it is inexpensive, you can take it apart without destroying the panel, and you can find it anywhere. The question came up about if the aluminum was a structural element in the rigidity of the car, and the answer was that the silicone works. The only advantage to some of the adhesives is that you can reduce the rivets used. As far as using epoxy, this would be higher in price and more difficult to get a clean result than some of the other alternatives from 3M. I hope this helps.

[Studebaker396]

Thanks. Your points make sense.

[mikeinatlanta]

When curing, most RTV silicones release chemicals (such as acetic acid) that are corrosive to aluminum. Silicone does not take paint. Silicone is too flexible to allow any of the strength of the aluminum to stiffen the frame it is riveted to.

For these reasons, I use products designed for bonding panels being installed permanently and sealing products for panels that may need to be removed one day. When caulking around my bathtub silicone is fine. IMO, window and bathtub sealer is no way to build a car.

Pulled the skins off a car trailer I bought when it was about two years old. 100% of the silicone was no longer bonded to the trim and aluminum panels, it fell off as I took the screws out.

[Studebaker396]

Do you have brand names of these kind of adhesives and sealers that you use? As I stated in my original post, I'm not sold on the silicone. But, FF has it in the kit?

[mikeinatlanta]

I use mostly 3M, but suggest going to your local auto body supply and getting the brand they carry. The two I use most is 3m panel bonding adhesive (automix) and 3m seam sealer. Both are paintable.

EDIT: I'll add that both cost way more than bathtub caulk, and for good reason.

[AC Bill]

I wonder if brush-able seam sealer would work as an adhesive?

It certainly is tough stuff when fully cured. Waterproof, and paintable. It would be easy to apply, takes a little time to set up, so is forgiving if you need to adjust something. If you had a quart can, you could use it as needed, and re-seal it. Epoxy can be tricky in that regard, as well as it cures quite rapidly...Just a thought..

[mikeinatlanta]

I wonder if brush-able seam sealer would work as an adhesive?

It certainly is tough stuff when fully cured. Waterproof, and paintable. It would be easy to apply, takes a little time to set up, so is forgiving if you need to adjust something. If you had a quart can, you could use it as needed, and re-seal it. Epoxy can be tricky in that regard, as well as it cures quite rapidly...Just a thought..

While not rated as such, certainly an upgrade from silicone. Seam sealer in a tube is much easier to work with at a small increase in cost.

[GoDadGo]

Paint or powder coat your pans or leave them natural if you like.
Just use a thin bead of high-grade silicone all weather or marine clear sealant when you attach the pans together.
It stops rattles and makes a nice seal and doesn't look bad if you wipe off any excess (quickly) during the installation.
Don't overthink this process and all will be right with the world!

[toolerwayne]

I used a product a
called Syleprene. It is a urethane seam sealer sold by Trailmobile used in constuction and repair of heavy trailers. It comes in white or gray. Strong and flexible but smelly and fast setting. I used to stock it in my shop but the shelf life is poor. You can get it at Fleet Pride. Now I use a 3M product from Napa called Dynatron. Same qualities, but better shelf life and working time. Also comes in gray and cleans up with solvent while wet.

https://www.napaonline.com/napa/en/p/MMM550/MMM550

I used silicone on any panels I might remove later

[michael everson]

I'm with GoDadGo. You guys are overthinking this. Silicone works just fine. I really don't think the epoxy or other stuff is going to add any strength. What does a stronger bond on something like an aluminum panel gain you?
I have taken a few older FFRs apart that were siliconed. Some of the panels were near impossible to get off without damaging them.
Mike