epoxy bonding metal to metal

[zzebby]

The 34 coupe is out getting some work done so have moved on to an old project from the sidelines.
Have a dash that is normally spot welded to the firewall structure,  but had problems with rust where the spot welds were.  I have redone the area and cut out / replaced all the rust and have a new dash to go in.  If I weld it in then rust will restart in the welded areas.  I know there is some 3M  weld thru no rust goop but I'd prefer to use some of the structural adhesives that new cars are put together with.  That way I can weld the ends and paint that area (POR15)  and use the epoxy for the main part of the dash.  This will seal it plus there will be no paint burned away for rust to restart.
Any recommendations on the "goop" ?   One part epoxy or two part ??  Polyurethane or epoxy or ?   Have tried the home depot construction adhesive like liquid nails and it is a maybe but wanted some first hand recommendations

[Bob Paulin]

Look into the Loctite/Devcon "Plastic Welder", two-part epoxy. It is available at a number of retail automotive outlets and at some of the "Big Box" stores.

It has a 3500 pound adhesion strength.

I used it to re-close and seal up some shock absorbers I had cut open, and we ran them for a few races on the race car with no apparent failure due to pressures, stresses and/or oil.

I spoke with one of the engineers at Devcon, told him what I was doing, and he said that the "Plastic Welder" - with proper preparation (no oil, etc.) - would do the trick......I believe he was correct.

IIRC - Devcon is in Everett, Mass. and manufactures a LOT of the epoxy that is marketed under different brand names (I got sent there while researching Loctite epoxies)......so, if the package says "Plastic Welder" and advertises a 3500 pound strength it is, most likely, a re-labeled Devcon product.

Like everything else, success is the result of preparation.

BTW - the "Plastic Welder" is the only readily available epoxy that I have found that actually works with plastics such as ABS - and it says so, right on the package.

I used to sell a lot of it to snowmobilers to repair their machine's ABS plastic cowls.....usually after they had found a tree stump that had been carefully concealed in a snow bank.


B.P.

[zzebby]

Thanks Bob.
Yes I clearly remember those trees and boulders that jump up out of the snow and how easily those cowls break.  Bombardier sure loves them.
But really I'm looking for feedback on sheet metal to sheet metal bonding using a structural adhesive such as epoxy or polyurethane.
I will check their website for this info,  but need input from someone who has done this.

[Skip]

"Structural adhesives" is about an accurate a statement as "military intelligence"

When these first came out, they were touted as the best thing since sliced bread and, supposedly, were endorsed by the maor auto manufacturers.

Soon afterwards, however, they proved unreliable.

We've had a number of vehicles come into the shop (I don't work for Compaq any more, I work at a collision repair shop) that were "repaired" with "structural" adhesives.  Taking them apart is a LOT EASIER than taking apart a spot welded panel.  All you need to do is slip your pocket screwdriver into a gap and simply pop it off.

Once the glue hardens and the vehicle goes through a seasonal temperature cycle, the panel will pop off.

[nzsimon]

My guess is windscreen urathane is what you are looking for they don't fall out and what gets more extremes than the screen it is black as well

[Bob Paulin]

Thanks Bob.
..........
But really I'm looking for feedback on sheet metal to sheet metal bonding using a structural adhesive such as epoxy or polyurethane.....

Perhaps the name "Plastic Welder" is throwing you off.....

It IS a two-part, metal-to-metal, 3500 pound strength epoxy......I believe they derive the name from the fact that it is a "plastic" component that "welds" things together......

.....and, as I pointed out,  it worked well for me under the pressure, heat and other racing conditions on tubular, steel automotive shock absorbers.

It just so happens that it also works well on plastics.....but, I don't think that was the primary design concern.

Call Devcon and speak with one of their engineers....

B.P.

[zzebby]

The windshield urethane sounds like the easiest way to go and a lot less mess.  Will post when I get it done , a week or two.
The devcon also appears that it will work, though Skip's comment is hard to doubt.  I was asking for experience and he speaks with conviction.

[Mr Cool]

Over here we have a product called Sikaflex. I dont know if its called the same thing over there. Its in a tube dispenser that fits straight into a standard caulking gun just like liquid nails etc.
Its used extensively in the automotive industry, the late 80s-early 90s holdens had the entire firewall glued in with this stuff. rain gutters are often sealed and stuck together with it. Almost every bus on the road uses the stuff to hold the side panels on rather than rivets.
Ive used it to mount/seal solar panels onto motorhome roofs (with the aid of bolts just in case) however I know of others who just use the Sikaflex only.
Its really good stuff and sticks like nothing else that I know of. very difficult to remove once it has dried properly.

[rumrumm]

3M makes several versions of a two-part epoxy. The one I have used bonds fiberglass to fiberglass or wood to fiberglass. It worked very well for me when I was building the '32. But it is not cheap--about $35.00-40.00 for the stuff. There is one version that is used to bond metal to metal.

[34ford]

Here's there site:

http://www.sikaindustry.com/ind/ipd-transoem-body


Here's where to buy it:
http://www.jamestowndistributors.com/find;a;1;ID;,Sikaflex.Caulks;eclDrill;648

[enjenjo]

I've used Sikaflex, excellent product. It's great for sealing wheel tubs.

[model a vette]

Another product is Fusor @ www.fusor.com.

[docchevy]

Right!  I've used Fusor in several flavors and they work great.  Just remember to rough up the material before you try to glue it.  So many people just smear it on and expect it to hold.  It's also useful to glue fiberglass panels together without the mess and the runnyness (is that a word?)  Be careful it sets up quickly!

[zzebby]

OK  the choice is between Sikaflex and the windshield urethane. Price is about the same even with the windshield guy service call but with him there will be an extra set of hands to set the dash into the wet goop.  I've just sprayed the firewall / cowl area with POR 15 after welding up the rust holes so I will be bonding to that.  Should it be scuffed ?   It is fresh paint,  but not level or smooth.  There will be some gaps,  maybe 1/8  or even 3/16 of an inch   so this makes me think the windshield urethane would be best.
I cannot spot weld it in place as then the rust will just eat it again.  I don't have a spot welder anyway.  The ends will be welded in as there is access on both sides to repaint the burnt areas.  Where the dash joins the cowl allows no access to repaint or treat after the weld burn.
Could Skip weigh in again??

[model a vette]

I would test a scrap piece with POR15 on it. POR15 is pretty smooth. I would rough the POR15 surface in any case.