VCCA Home Forums TECHNICAL - GENERAL Body - Sheet Metal, Paint & Wood Undercoating on 1940 body

The guy doing the body work on my 41 has a 1940 Master Deluxe. It has been in the family for about 50 years and is unrestored. He found the material shown in the following pictures on the inner fenders, frame, and body and is wondering if GM or its dealers might have used any undercoating on their cars back in the 40's?

Does anyone remember when undercoating became a dealership option or a popular way to control rust. I seem to remember Ziebart being popular in the late 60's and 70's? There web site says they have been around since 1959.

Thanks, Mike

P.S. I do remember that the factory sprayed an asphalt type material inside my doors and over the interior wheel well area as a sound deadener, but I assume not for rustproofing!

man Mike that's some nasty looking stuff...Would hate to get any of that on my parts underneath

After WWII undercoating the car was very poplar and profitable for dealers. The material was not available from Chevrolet until 1949. It was considered a "service accessory" accessory # 986359 and sold in 55 Gal. drums. It was sprayed on. Prior to WWII Chevrolet did sell an "under fender" sound deadner material that could be brushed on.
If the pictured material , which has the texture of spray on material, probably was done to the 1940 some time after WWII.

I think that local undercoating was more pervasive than Chevgene is suggesting. While in high school in IN during the early '50s, I worked evenings in a Std Oil station and steam cleaned the underside of cars, and then sprayed a petroleum based undercoat on the underside of the fenders and the car body. I remember people bragging about having their cars undercoated. That was, until they found out that, usually, the metal kept right on rusting under the undercoating.

My '51 was covered in that stuff. Very popular up here in Canada. All of the floor pans, and central areas of the bigger parts were really well preserved, even with factory grease pencil markings showing. The outer edges and corners of any sheet metal had rusted though. The undercoating seemed to be a lot thinner on the edges.

Just to add a bit on to Brewster's reply, his '51 saw very little driving in the winter months in its life, thus had very little exposure to the salt/slush of Ontario roads . Brewster's grandfather worked at the Chev dealership where the car was purchased new, and made sure that it received the best undercoating that his shop workers could apply. Grandpa had also purchased a new '51 in January and had it undercoated as well. That car was the family car, hence saw much winter usage. By 1956, the rockers were rusted out, the front fenders had holes behind the headlights you could put your fingers through, and the rear fender skirt openings were completely gone - rusted away. Why? The undercoating that came in those drums dried out and cracked within a couple of years after application. Water(and dissolved salt in winter) easily found its way between the undercoating and body metal. The end result was the undercoating did the exact opposite job it was meant to do.

Number 1 mistake was to spry on an extra heavy coating.....was supposed to be about 1/8" thick.
The undercoating just covered the external surfaces. Most rust began from enclose areas where water could penetrate.
The first factory use of undercoating was in 1949. The rear wheel houses had a thin coat, mostly for noise reduction.

Hello Chevy Gene and all else,
Was this undercoating used through 1958? I just question this because of what I heard about the 1958 Chevrolets and the absence of inner fenders. I understood that the salt and slush stayed up inside and ate away, rusted the top side do the fenders. Poking your fingers behind the headlights and the tops of the front fenders.
Gus Gillespie
1941 Master Deluxe.

The 1962 was the first to have a full inner front fender.
Prior to that there were rust pockets exposed in the front fenders like above the head lamps, etc.

I have that same type material under my 52.

I have been scraping large sheets of it off with a small putty knife. Where I am going to have problems is around the brake lines, fuel lines, and small areas where it built up. I have to admit though that the panels under it are still very clean, the paint still shines.

I have a feeling that is because my car originated in California and was never driven in salt.

Jim