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View Full Version : What exactly is the undercoating made from?



JimC
05-13-2012, 12:56 AM
Hey experts and others generally smarter than I (which I believe is 99.98% of y'all):

I've been wondering this since the first time I started trying to chisel it off the body of my cars. What exactly did Studebaker make their undercoating out of? What's the favored replacement? (Hopefully something a little more effective against rust!)

52 Ragtop
05-13-2012, 09:31 AM
When I would (properly) dispose of the hazardous waste from the paint shop, I was told it was cleaned and resold as "wash thinner" and some (I'm assuming the thicker waste) was recycled into undercoat. But, don't take that as gospel!
The undercoat was not the problem that Studebaker had, it was the improper treatment of the steel. and the fact that nobody expected these cars to be around 50 years after their demise! <G>
But, properly prepared metal, a good e-coat primer, (etching primer) a 2 part primer, and a good couple of coats of paint, along with the car going to live a "cherished life" they will probably outlast all of us!
I think on my 64 ragtop, once the underside is cleaned and painted, I'll be spraying truck bed liner in it, and hit the inside too.

Jim

starliner62
05-13-2012, 09:52 AM
Undercoating is something the devil manufactures to make us say bad things when trying to remove it.

Milaca
05-13-2012, 10:36 AM
It's been my understanding that the undercoatings main purpose was for sound deadening and that it is an asphalt material. What is asphalt made of? The following information copied from Wikipedia:

Asphalt, also known as bitumen, is the sticky, black and highly viscous liquid or semi-solid present in most crude petroleums and in some natural deposits; it is a substance classed as a pitch. Until the 20th century, the term asphaltum was also used.

The primary use of asphalt is in road construction, where it is used as the glue or binder mixed with aggregate particles to create asphalt concrete. Its other main uses are for bituminous waterproofing products, including production of roofing felt and for sealing flat roofs.

The terms asphalt and bitumen are often used interchangeably to mean both natural and manufactured forms of the substance. In American English, asphalt (or asphalt cement) is the carefully refined residue from the distillation process of selected crude oils. Outside the United States, the product is often called bitumen. Natural deposits terminology also sometimes uses the word bitumen, such as at the La Brea Tar Pits.

Naturally occurring asphalt is sometimes specified by the term "crude bitumen"; its viscosity is similar to that of cold molasses. whilst the material obtained from the fractional distillation of crude oil [boiling at 525 C (977 F)] is sometimes referred to as "refined bitumen".

comatus
05-13-2012, 12:44 PM
Known as "tore" to all of us. If you ever look at engineering specs for blacktop, surprise! It is asphaltic concrete, and available in many formulas, which is why you go to engineering school. Tar and stone chips is formally "tar-bound macadam." A stone road with large berm under, mixed sizes over that, and screenings on the top is "water-bound macadam." In olden times, paving a road was called "metalling." There's some irony (get it?) in that, since roads un-metal whatever's on them.

That's right about sound deadening over metal protection, and many will recall having that stuff fall off in chunks. There was a kind of scandal in the history of Ziebart when they improved the mix with plasticizers for better adhesion and waterproofing. Big Tar was scandalized. Real car guys, of course, just sprayed them with drain oil. Yep, Studebaker thought of everything.

I have an old car buddy who runs a Ziebart shop, so I still use it, and believe in it, up to a point. Fallingwater House belonged to a merchant named Edgar Kaufmann, and when Mr. Kaufmann complained to Frank Wright about it (he called it Rising Mildew) leaking and flooding every year, Wright told him "That's what happens when you leave a work of art out in the rain." Wright was just awful that way.

Tony Lago to Lord Beaulieu, on the Talbot overheating in town: "Well, if you insist on abusing the vehicle..."

new2drive
05-14-2012, 06:08 AM
Comatus is correct... applied "warm" it then hardens into an awesome coating. Being a petroleum chemist, I understand it's general make up pretty well. To really get the stuff off best, you have to soak thatever is coated in thinner/turpenteine, etc... probelm on cars... you really cannot soak them. I would suggest getting a 5 gal pail of paint thinner and brushing it on or spraying it on. One thing.... this will be VERY messy and slow if you really want to get it off without damaging the parts. DO it on a very hot day too... it is easier to coem off then.

If you need to get into some details, pm me. I deal with this sort of stuff all of the time at work (I have to remove this tar type material from meters in the field.

TX Rebel
05-14-2012, 08:01 AM
Heat is my preferred method of removal for stubborn coating that won't peel or scrape off. It is better to heat the metal from the back side if possible.
Gasoline cuts it pretty well, but use it outdoors only with proper safety precautions.

hausdok
05-14-2012, 11:04 AM
Hi,

I got it off with a propane torch. Blanch it just enough to soften it but not to ignite it, and then it sloughs right off with a putty knife. You have to be quick. When it cools it hardens right up again. Best to keep a fire extinguisher nearby just in case.

I guess my question would be; since undercoating was original equipment, if one is restoring a car to original condition and intends to show it, must one use the original asphalt-based undercoating or could one use one of the modern liquid rubber undercoatings instead and not get docked points?

jlmccuan
05-14-2012, 12:34 PM
Heat is my preferred method of removal for stubborn coating that won't peel or scrape off. It is better to heat the metal from the back side if possible.
Gasoline cuts it pretty well, but use it outdoors only with proper safety precautions.

After my past 3 months experiences, I can categorically state there is NO safe precaution for using gasoline for this purpose. I have the pictures to prove it if necessary...

Studedude
05-14-2012, 12:45 PM
After my past 3 months experiences, I can categorically state there is NO safe precaution for using gasoline for this purpose. I have the pictures to prove it if necessary...

Thanks for pointing that out, Jim!

I cringed at the thought of using thinners or gasoline, followed by the application of heat.

Let's be careful out there!

2r10jim
05-14-2012, 12:54 PM
I bought a Wagner heat gun with two heat settings at Walmart for about $30. I have used that for removing the undercoating on my 1969 Mustang Fastback. It worked great and it will safer then using a open flame or gas. You still have to use caution however. After the large stuff was removed I then cleaned the metal with a rag and carburetor cleaner (no heat was applied during this step).

drew72mgb
05-14-2012, 03:15 PM
I stripped the bottom of my MGB with a heat gun, and putty knife/paint scraper. A film was left - a thin layer of gunk which filled a wire wheel attached to a drill with crap and made it useless. I then used Scotch Brite pads soaked in mineral spirits - out doors with rubber gloves - it was messy, but it all came off.

The underside was primered with a 2-part epoxy primer, sealed with a urethane sealer (used a plastic spoon to smooth seams). The next layer was Shutz - Rocker Shutz - a 3M product - it is a pebbly grained finish - anti-chip coating. A sealer was sprayed on top - followed with a urethane 2-part paint.

I am very surprised - 6,000 miles later - the underside is chip-free. I do avoid gravel roads, and the 2-3 times I have driven a mile on gravel - I have done it slowly...

Drew

johnod
05-14-2012, 08:38 PM
I think the heat gun works fine, got a milwaukee, surprising how fast it heats stuff. Gets most of the stuff off.

woodysrods
05-15-2012, 12:29 AM
I stripped the bottom of my MGB with a heat gun, and putty knife/paint scraper. A film was left - a thin layer of gunk which filled a wire wheel attached to a drill with crap and made it useless. I then used Scotch Brite pads soaked in mineral spirits - out doors with rubber gloves - it was messy, but it all came off.

The underside was primered with a 2-part epoxy primer, sealed with a urethane sealer (used a plastic spoon to smooth seams). The next layer was Shutz - Rocker Shutz - a 3M product - it is a pebbly grained finish - anti-chip coating. A sealer was sprayed on top - followed with a urethane 2-part paint.

I am very surprised - 6,000 miles later - the underside is chip-free. I do avoid gravel roads, and the 2-3 times I have driven a mile on gravel - I have done it slowly...

Drew
Nice to see someone doing the underside of their car "Right Way" not the "Cheap Way"
We do all our restorations with the exact same steps as above. NEVER had a come back!
Good Roads
Brian

woodysrods
05-15-2012, 12:31 AM
For "old hard" undercoating, an air chisel with a dull blade at an angle works great. It almost vibrates the undercoat off.
Good Roads
Brian