Small floor patch panels with epoxy instead of welding - any reason I shouldn't?

As my E28 project continues I've found a few soft areas in the driver's floor pan. It's rotted out where the gas pedal mounts to the floor, which is super common, and also at an area where the PO nonsensically jacked into the floorpan. I shouldn't need any more than two 4" or so patches as everything else is solid.

Now the fuel lines run right under this area and I also have no ambition to weld in general. Since I'm just adding a few small patches to an otherwise solid pan instead of replacing the whole pan (in which case welding would be the obvious solution), is there any reason I can't get away with just using bonding epoxy? My thought is that with good prep and finish work it should work just fine and nobody will ever know the difference. Thoughts?

I see no problem but if it were me I would throw in a few pop rivets to make a mechanical connection along with the chemical one. In fact I have repaired many a floor pan of older cars with sheet metal and pop rivets alone. Just using some sealer at the seams to keep out water and they held up fine.

Back in the early 90's I had a piece of road debris punch a hole in the floor of my 3 month old Chev. From the underside i bonded a patch using Sikaflex 221. I ran that car summer and winter for over 10 years with no problem.

As someone who recently discovered a half-assed patch job in the floor of a car, I'm biased when I say you should do it the 'right' way.
But most any other time I'd side with Jim, include some rivets.

Ive patched trunk floors with pop rivets and some silicone around the edges. Im not sure id go epoxy alone.

If it's a small patch, depending on what's around it, it might actually be easier to get a solid patch that's protected from future rust at the seams with some combination of rivets and epoxy. Worst case, if it doesn't come out well, you can always cut the patch back out and weld one in.

jimbbski wrote: I see no problem but if it were me I would throw in a few pop rivets to make a mechanical connection along with the chemical one. In fact I have repaired many a floor pan of older cars with sheet metal and pop rivets alone. Just using some sealer at the seams to keep out water and they held up fine.

If you use good seam sealer, you won't need the rivets.

BTDT.

I've also seen repair jobs that used fiberglass resin as the adhesive and sealer that turned out remarkable well, with "well" being watertight and permanent, which is all that matters isn't it?

This is what I did to SanFord. Galvanized sheet metal, NP1 and drill and tap screws.

I have done it using moisture cured urithane construction adhesive made for metal. This is important as you need a great bond but you have to be able to move with the expansion and contraction of the metal. It is used to bond new cars together. Let cure for two weeks and then seal the perimeter with either np1 or demonic FC. The most recent one was the patch under the battery in a 944. When I am done you can not tell the repair was made as there is so much seam sealer used th that area.

Thanks all. It sounds like I will be just fine for my really quite small patches going the adhesive route.

POR-15 makes a seam sealer, maybe I will give that a try. Or can someone else recommend a product? Dean, I was thinking along the lines of what you used (actual panel bonding adhesive made for the job) but I'm having a heck of a time finding the right stuff.

I did the rocker repair on my son's Exploder using a new patch panel held on with epoxy and some big pop rivets. It's only been about 8 months, but it looks like it's holding up well so far.

Glue it and screw it, better Living through chemistry . Adhesives nowadays really are rocket science.

Adhesives these days are in many cases have a bond that is stronger and are materially stronger than the material being stuck together.

dean1484 wrote: Adhesives these days are in many cases have a bond that is stronger and are materially stronger than the material being stuck together.

A few years ago a friend sent me photos of where the sheet metal tore but the adhesive stayed put. Awesome stuff, and it doesn't burn the paint off like welding. I totally say glue it. Besides... how many cars are running around with rotten floor pans and do just fine for years? Not like an structural integrity will be lost either which way.

if you can build an ocean going boat out of epoxy and glassfibre, you can do a small patch on the floor of your car.

Definitely use glue on it ! I buddy glued a rear quarter on his "55 Ford. It's been there for years and still in perfect condition.

There's a wonderful "paint" called Masterseries ( http://masterseriesct.com ) that's used for rust. It's honestly an amazing product with an almost 40 percent aluminum dust percentage. There is ALWAYS an aluminum "fudge" concentrated at the bottom of the can. Those in the know, tape up the bottom of the rusted floors in their cars and spread the "fudge" over the top side. Works PISSA ! !

I did a couple patches bigger than that in the trunk of my Prizm a few years ago with pop rivets and PL Premium, they're still there and solidly attached last I checked.

Something like Eastwood's No Weld Panel Repair Kit?

The one thing that would concern me about using a method like this for a floor is the panel is essentially exposed on both sides, vs most applications where the back of the repair is cavity space. I've seen this done on a couple of vintage Volvos and it can look OK on one side, but like crap on the other.

My M535i had the same problem as the original poster but it wasn't apparent at first. The undercoating on the bottom was still completely intact, so you couldn't see the rusted out spot from underneath. Only after the carpet was pulled up could I tell there was any rust at all. The little tab that the base of the gas pedal snaps into was completely gone, we had to fabricate a new one from scratch.

That spot is not structural at all, so one of the new body panel adhesives should work fine if welding is not an option.

dean1484 wrote:

This, maybe a couple screws to hold it until it cures but the adhesive alone should be plenty.

My Dart has a few small (about 2 square inches) holes in the floorboard patched with epoxy-soaked cloth. The patches have held on so far for over 20 years.

I just did a rocker repair with galvanized steel and jb weld. So far,  so good.