Interior Cavity Rust Protection?

I've never bothered to protect the hidden, inside surfaces of body sheet metal cavities (like rocker panels) but now that I am welding the cage bits into the Manta, and since it's getting harder to find those bodies, I am thinking about trying to do something to protect the inside of these cavity areas. You know they have to rust after all the paints gets burned off when welding?

Any suggestions on the protection to use, and how to apply it? And thoughts on when to apply? Like after re-painting is complete on the exposed surfaces? Linseed oil comes to mind, but I would have to wonder about flammability.

Thanks,
Mark B.

Waxoyl?

What about body cavity foam or whatever that stuff is called that some automakers use. It could have the double effect of sealing the cavities and providing exta structural strength.

I assume that the foam is for sound deadening? As such, I would not necessarily expect it to be water repellent, and might act to absorb and/or hold moisture against the metal. I really don't know fer sure, but filling the cavity seems to be a way to insure that is does not dry out when water does get inside. (Kinda like building construction: insuring a free flow airpath through all exterior caivites is a must.)

Regard,
Mark B.

I agree with you.. there is also the flammability issue. Starting a wee bit of fire with some rust proofing is one thing.. Foam, I'd rather not.

I think your biggest problem will be getting to the areas that got welded.. as they are going to be on the same piece of sheet as you would have/make your access holes. Not impossible of course.

You might not win that battle without acid dipping the body.. as it's quite likely there's rust there now.. if not from before, from the welding.

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Andrew M
Onterrible
30ish

And what about when you decide to weld a tab to your rocker and you ignite the stuff underneath, that foam spray stuff is stinky when it burns.

Dooooood!
Does a coffee cup absort your coffee?
Its the same stuff but denser.

When I read in FIA rules a long time ago "Unless it original, it is prohibited to fill cavities in Gp balh blah"
If they're prohibiting it (and Ford is suggesting doing it if the rules allow) then it must be good.

I have and it works fine.
The body parts become in effect a composite, mucho stiffer.
I've done the sills and the box longitudinal stiffeners and the cross stiffeners.

From one point of view the close cell foam EXCLUDES dirt and water from getting IN since it's there in the first place..

---

John Vanlandingham
Sleezattle, WA, USA

Vive le Prole-le-ralliat

www.rallyrace.net/jvab
CALL +1 206 431-9696
Remember! Pacific Standard Time
is 3 hours behind Eastern Standard Time.

Mark, the foam I am talking about is actually structural. I do not know about how flamable it is but I know that like John said it is creates extra chassis stiffness. I would assume that it is waterproof as well. I know that Infinity used it back in the day. Also, Plymouth used it in several places on the prowler that needed to be stiffer than the aluminum frame design would allow.

Andrew



Edited 1 time(s). Last edit at 04/15/2008 02:02PM by Andrew_Frick.

CorrosionX is a product that is used to keep Airplains from falling from the sky, esp float planes that land and take off in stalt water all the time. The stuff rocks, it creates a fog that gets everywhere via any opening you have into the space. On the plane it getts applied once a year.

http://www.corrosionx.com/

Boeshield is another but all my mecanics like the CorrosionX product better for some reason.

Derek

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In the long run reality always wins.

CRC's heavy duty corrosion inhibitor is a wax-oil aerosol. cheap and easy rust prevention for inner bits.
Per

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Per

Thanks everybody, for the info and inputs. I think I will go with the sprays, as I suspect I will eventually be weldeding someting over these areas sooner or later.

Regards,
Mark B.

Mark, my Ascona had pretty much no rocker panels left at all, so I built them from scratch. I used the weld-thru primers on the inside and let it dry fully before welding. Sure, some of the stuff burns away, but it's got to be better than 100% raw metal.

Bob

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Opel is a 4-letter word...
http://www.flickr.com/photos/10498579@N07/sets/

john vanlandingham Wrote:
-------------------------------------------------------
> Dooooood!
> Does a coffee cup absort your coffee?
> Its the same stuff but denser.
>
> When I read in FIA rules a long time ago "Unless
> it original, it is prohibited to fill cavities in
> Gp balh blah"
> If they're prohibiting it (and Ford is suggesting
> doing it if the rules allow) then it must be
> good.
>
> I have and it works fine.
> The body parts become in effect a composite, mucho
> stiffer.
> I've done the sills and the box longitudinal
> stiffeners and the cross stiffeners.
>
> From one point of view the close cell foam
> EXCLUDES dirt and water from getting IN since it's
> there in the first place..
>
> John Vanlandingham
> Sleezattle, WA, USA
>
> Vive le Prole-le-ralliat
>
> www.jvab.f4.ca


Could I please learn a little more about this foam? What are you using, experiences, how do I learn more, etc?

---

james phillips
Volvo 242 GT (being built...)
Scooby killing 04 Dodge Neon SRT Rallycross monster
Lincoln, NE

john vanlandingham Wrote:
-------------------------------------------------------
> Dooooood!
> Does a coffee cup absort your coffee?
> Its the same stuff but denser.
>
> When I read in FIA rules a long time ago "Unless
> it original, it is prohibited to fill cavities in
> Gp balh blah"
> If they're prohibiting it (and Ford is suggesting
> doing it if the rules allow) then it must be
> good.
>
> I have and it works fine.
> The body parts become in effect a composite, mucho
> stiffer.
> I've done the sills and the box longitudinal
> stiffeners and the cross stiffeners.
>
> From one point of view the close cell foam
> EXCLUDES dirt and water from getting IN since it's
> there in the first place..
>

Actually, you might think that buts it's really quite the opposite. Moisture will get into it and the foam will hold it there. Eventually you will see rust bubbles forming that will have started between the foam and the metal. Once rust starts and takes hold the only way you can stop it is to cut it out entirely. There is nothing you can put over rust that will stop it from spreading. Oh, you can slow it down for awhile but eventually it will keep spreading underneath whatever you put over it. I am speaking as a guy who used to paint cars for a living and worked in a restoration shop cutting rust out of old creaky British cars. I repeat, the only way to get rid of rust is to cut it out!
Having said that the closed cell expanding foam can add stiffness but you should only use it in a rocker, for example, after you have fixed any rust and fully primed, painted, or rust treated the interior of the panel. If you just spray it into a bare metal rocker, or worse yet, an already rusty one you are just going to accelerate the cancer.
Also, the stuff is extremely flammable and will ignite really fast. Forget about ever welding on a panel with it on the other side. It will ignite and you will have a lot of contamination problems welding it. If you somehow successfully weld the panel then it will eventually rust there for sure.
Bob's Capri had that stuff all in the rear wheelwells and rockers and it was a big problem. I had to dig all of that crap out of there in order to install the fender flares and repair the rust that it caused.
I wouldn't use the expanding foam in a race car myself. The benefits do not outweigh the problems, IMO.

Just some things to keep in mind.

I think you guys are talking about two different kinds of foam.

The stuff you find in modern cars (Infinit Q45 A-pillars, some RX-8 front crossmembers, etc) is a 2-part closed-cell epoxy foam that is rigid as hell and bonds to the medal, so water can't get between the metal and foam. The fact that Dave is talking about scraping the crap out suggests he's talking about something softer that actually CAN be scraped out.

I'm also not sure about the flammability of the epoxy stuff. I filled a test piece and was going to weld to it to see what happened, but I lost track of the piece...

I have some of the foam somewhere in my garage. When I find it, I'll post the info.

-Dave