Undercoating Vintage Volkswagens

Undercoating Vintage Volkswagens

Digging in the archives here at 1967beetle.com, we wanted to put this article in the spotlight once again.

Foreword: Rather than to address “undercoating” as a general topic of discussion, I’ve tried to keep the focus upon undercoating as it related to Volkswagens through 1979 and as it relates, now, to the vintage Volkswagen hobby.

Undercoating has around for years and years in the world of vintage Volkswagens.

The theory behind undercoatings is that a barrier could be created to prevent the infiltration of moisture. Undercoatings themselves had no rust-inhibitive qualities. They simply have been intended as a barrier.

VW dealerships sold the service to new car buyers as a preventative measure to guard against rust. It was a money-making operation and dealers loved it. Especially was it offered in the colder climate States and especially where salt was used on icy roadways.

Recently, I spoke with a former VW trained specialist. He described the undercoating procedure as he observed it. He said that the dealership where he worked had one bay with a lift, “in a dark corner”, where the “nasty” undercoating took place. He told me that it was part of a money-making effort by dealerships in the make-ready department. Undercoating was applied using a hose and gun working from a 30 gallon barrel of material.

I have had my doubts over the years about its effectiveness in sealing the undersides of a vehicle as a moisture barrier. Here’s why. I was in the painting industry for almost 30 years. If there is a coating, I likely have seen it or read about it. In my experience, despite all claims to the contrary, coatings will fail. There is no “eternal” coating. I’ve heard claims that “you’ll never have to paint again”. Why can’t this be true?

Undercoating Vintage Volkswagens

It can’t be true because of expansion-and-contraction problems. When the base material—wood, metal, plastic—expands or contracts, the coating is going to suffer, eventually. Some coatings are better suited than others. But the fact of the matter is that coatings fail.

Metals, especially, are given to fluctuations from heat and cold. They will expand and contract more, and more quickly, reacting to weather and usage conditions.

What’s another problem? It’s the fact that the underside of a vehicle is not a continuous sheet of metal. Not at all. The undersides of vehicles are composed of pieces that have been fitted to form a unit. This could be through a continuous weld or spot-welding or with nuts and bolts and washers. There are joints. Every place where there is a weld or a nuts-and-bolts joint, expansion rates will differ.

As well, the application of undercoatings must completely encase all of this in order to form a viable covering—it must be seamless. This doesn’t happen.

The next issue is that undercoatings historically were shot onto factory painted surfaces. In order for a coating to adhere, there must be the possibility of adhesion. Slick surfaces will not offer such adhesion possibilities. As a result, I have been able to remove portions of undercoatings on Volkswagens simply by using compressed air. Sometimes, I have been able to remove it in sheets, simply because of the lack of adhesion. I can imagine that vibration over the years helps to loosen poorly adhered coatings.

Also, the spraying of undercoating cannot reach all places and the places which it does reach often are coated unevenly due to the nature of the operation.

While coatings do not adhere well to many painted surfaces, they may adhere to other surfaces tightly—such as the transmission, the horn, shock absorbers, brake lines, etc., etc.—parts which need little protection. Now, these parts are covered –at least parts which the spray can reach.

Another factor to understand is that coatings shrink as they “cure”. Shrinkage does not happen immediately. Some coatings may take hours or even days to complete their “cure time”. Generally the thicker the coating, the longer the cure time. Shrinkage causes the under-coating material to pull away from the metal, especially where the under-surface is slick.

Undercoating Vintage Volkswagens

Undercoating Vintage Volkswagens

Undercoating Vintage Volkswagens

A good example of the detrimental effects of undercoating is a ’69 Beetle which came from Ohio. When a friend showed me photographs of a car which he was contemplating buying, I noted that the car was from Ohio and encouraged him to check the undersides. After the purchase, I had opportunity to examine the car. I found it to be an original car, except for a fresh paint job. The engine never had been opened, etc. The car obviously had been undercoated “in the day”. But, oh, the rust on the bottom of that car! Moisture, dirt and salt had gotten beneath the coating and rust was rampant. “Cancer” rust! Such as rusted-through shock towers, etc., etc. The undercoating had hidden the oxidation all of those years and it had escaped cursory examination.

I discussed undercoatings with two qualified automotive restoration specialists. With one voice they agreed that no one who is restoring a vehicle should use undercoatings. That changes the nature of the car. To restore means to return to factory condition. Factories which manufactured Volkswagens never undercoated their cars. The cars were primed with rust-inhibitive coatings, then finish-coated. VW was proud of the rust prevention program which it practiced—it was an advertising gem in their crown.

We talked, also, about those of us who do not restore our cars but who recondition them nicely. Again, it was agreed that undercoating adds nothing to a car which, in most cases, never will be driven in conditions where it would be endangered by poor weather conditions and, especially, salted roadways.

These specialists also noted that nothing is gained by undercoating any vehicle. They both said that it was better to be able to monitor a car’s condition. Undercoatings make that virtually impossible.

Then, for cars which reside in dry climates, undercoating never should be considered.

I follow sales of VWs in order to stay abreast of the market. It is not unusual to read copy which touts new pan installation which has been undercoated. I have seen repaired pans under-coated in order to hide poor workmanship. Such coatings always are a red flag for me. Undercoating never should be used to cover new welds and seams. Proper smoothing, rust preparation and painting never should be circumvented.

Last, but certainly not least—undercoating is a nuisance when something on the bottom of the vehicle must be visited or repaired. And, even though there are “better” undercoatings available today (such as the now-famous bed-liners), all prove to be noisome to the mechanic or body repair shop when it comes to maintenance and repairs.

In summary

  • Undercoatings never should be used when restoring a vehicle.
  • Nothing substitutes for maintaining a clean vintage vehicle and avoiding conditions where the vehicle could suffer damage from weather-related causes.
  • Undercoating adds nothing to the value of a vintage Volkswagen nor can it be proven to effectively protect the bottom-side of a vehicle.
  • Undercoatings never should be used to hide poor workmanship or damage.

Posted by Jay Salser

My wife, Neva, and I have been driving and working on VWs since 1976. In fact, we raised our family in these cars. Now, we are retired and enjoy VWs as a hobby. The ’67 Beetle always has been our favorite year. We own a '67 Beetle and a '68 Karmann Ghia.

  1. Fantastic article, Jay. I’d love to hear what other readers think. I’m sure there will be some good conversation w/ this one.

    1. Interesting!

      1. Hello, Frank…I have discussed the undercoating “dilemma” many, many times over the years. I decided that it was time to record my thoughts and just let them “hang out there”! So far, we’ve received a couple of good ideas/suggestions. jay

        1. I’m waiting for the all out argument..

          1. Ha, ha, Eric…Well…you’ll get no argument from me. I’m looking for suggestions which will by-pass undercoating–like powder coating and Quinn’s idea of monitoring consistently and using rust inhibitive (as Graham Patterson says) paints on bare areas after they have been cleaned. jay

  2. Richard A. "Dick" Diaz July 26, 2014 at 10:43 am

    I agree with Jay based on his research and expertise, but I wonder how “powder coating” parts on a frame off rebuild affect rust, etc. I see some sellers touting, “rottessiery restoration and powder coating” in their ads! Not sure if either make a difference, but sounds like it may! Looks good too! Would the use of a “Rhino Liner” type material as an undercoat be any different than the undercoating used in the late ’60’s by dealers? Being located here in Southern California the use of undercoating has never been a benefit, but it is always offered by the dealers!

    1. Interesting comment, Richard. I too have seen that advertised. Jay?

    2. Hello, Dick…I’m glad to hear that you continue to enjoy your ’67 Beetle Sedan in sunny California! What a life!
      Dick..I don’t like any kind of a coating–not even today’s “superior” coatings such as Rhino Liner (bed liner). Not only is it not appropriate for a vintage restoration, it also impedes subsequent work that may need to be done to the undersides of a vehicle. So–no, I don’t like these coatings. As to powder-coating–this is a painting process–a baked-on finish that it quite hard and durable and electro-statically, evenly, dispersed. When done to a pan, it’s done without all of the nuts, bolts and washers, etc. attached. The result is a continuous and solid paint coating finish that is going to last. So, yes, in my experience, I value that sort of a coating. I’ve seen it, when well-done, applied to engine compartment tins. A very durable finish. There’s no comparison between powder coating and undercoating (and other kinds of “over-coatings”). One is going to seal, adhere and protect the metal and the other one is an over coating. jay

      1. And the VW whisperer has spoken..

  3. Richard A. "Dick" Diaz July 26, 2014 at 12:35 pm

    Thanks Jay for your follow up discussion to my questions! I think I am seeing the light here! So, from someone who is is continually crawling under my ’67 Beetle and my wife’s ’70 Ghia I can see how trying to wrench a part that has undercoating on it would make even a simple job more complicated! In addition, what perception of undercoating protecting the underside would surely be compromised as soon as the undercoat was chipped away to expose the bolt head! Had I thought out my question about powder coating and Rhino Linner I think I could have answered my own question! As the late movie critics, Siskel and Ebbert would have voted, I vote a “thumbs down” on undercoating! Great article Jay!

    1. Thanks for reading, Dick! I’ve owned a couple of VWs which were undercoated at dealerships in the make-ready department–besides other experience with undercoated VWs. I’ve spent an inordinate amount of time trying to uncover what I needed to be working on. My latest acquisition, a Karmann Ghia, is causing me some consternation for the same reason. Slowly, I am uncovering the bottom of my car–if I live long enough, perhaps I’ll get done. LOL One of the cars, which was a Beetle, had had extensive repairs done to the passenger’s side and pan due to an accident. The repairs took place possibly in ’76 or earlier (according to history which I was able to learn). Undercoating was used to cover seams, etc. I used compressed air to blow off sheets of the material where it had been shot onto painted surfaces. So much for protection. jay

  4. There are a lot of valid points made by Jay on the topic of undercoatings. Over the years I’ve seen exactly what Jay’s describing with it peeling off.

    What I find interesting is that I grew up in S. California. I’ve owned and worked on many VW’s that were delivered and stayed in California their entire lives. I’ve NEVER seen a VW bug w/out the dealer installed undercoating in place on these cars. Now, the majority of these VW’s were bugs and from the mid-60’s thru early 70’s.

    I wonder if it was truly an ‘option’ vs. the dealers spraying all their inventory when it arrived as an extra revenue source. I’m not sure how the sales pitch worked when they were selling a VW in San Diego were the car would in all likely hood, never see snow. Clearly, it’s not exactly a rainy climate either.

    One point I didn’t see being addressed is that some undercoatings help dampen sound. I know the Rhino linings really use that as a selling point. If you look at high end, luxury cars today, most have VERY thick sound deadening material (though on the inside) through out the cars.

    1. Hi, Bill! Thanks for your input. All valued comments! I think that today, rather than to spray on bed liners, etc. for their sound-dampening qualities, restorers are finding liners (adhesive insulation padding, etc.) for the interior that are hidden beneath carpeting and headliners that are more effective and less nasty to apply. And, anyone can do it! You are right, from what I have discovered by talking around–dealerships made some quick bucks by doing “make-ready” things, such as spraying on undercoating. Hey–even today you can get “Tha Package” which can consist of things such as “Scotch Guard” for upholstery, etc. It’s gonna cost you! You can save by going to the local grocer’s to buy a spray-on can and do it yourself. It probably will be just as effective and certainly will be cheaper. jay

      1. Great feedback, everyone!

      2. From Graham.

        “Reference to the post by Jay

        Morning Jay

        As attached sample

        You are 100% correct in all details. I believe from experience that there is no viable alternative to Hard Work, paint Remover, Sandpaper and Hard Sweat

        Nothing is going to last, so you set out to achieve the longest possible panel / resto paint job.

        I attach a photo of how I go about this. Doing one small area at a time, no the bare metal stays open to the air for the least amount of time. I use several coatings of paint stripper and then sweat and scrape each layer off, finally using sand paper and finger blistering sweat and tears to get to absolute bare metal. I spray on a rust inhibiter ( note not preventative as there is no such thing) Once the entire inside and out is finished I then use high quality primer and paint, several layers each, rubbing back each tome for e velvet finish and then 3-4 coats of Clear on top

        You get a great looking finish that will last many years……..then maybe you do it again all over.

        Nothing less will do



        Perth Australia”

        1. Well, Hello, Graham–from Down Under! I hope that you and yours are doing well these days! Yes…we used to say in the painting industry–“It’s all in the prep!” You make a valid point about having to redo the bottom-side (or any part of a vehicle) “down-the-road”. A restoration isn’t forever. It WILL need to be redone at some point. If there is undercoating that is peeling with rust beneath it–it is going to be many times more difficult to remove in order to repair the problem areas than were the whole painted. I have been watching the progress of the restoration of a ’70s American car which someone undercoated. What a mess it is–and extremely time-consuming. You can’t simply media-blast to remove that stuff. I have to add that this vehicle was undercoated with more modern material during an “up-date” which a previous owner did. Hey…I’m still looking forward to seeing your ’67 restored to its former glory, Graham! jay

  5. In theory, I believe most of what is presented in this well researched article but in practice, I truly believe undercoating has it’s place. In the north east, or anywhere they salt the roads, any nick, scratch or dent that may occur on the underside of your vehicle will be an open invitation for rust to begin. It may not happen overnight, but within a few years, that exposed metal becomes a rusty hole. When these vehicles were sold new, it was totally impractical for your average VW buyer to periodically inspect the underside of their car. It’s also a fact that your average buyer rarely held onto them for 10+ years. So if undercoating helped protect a car for at least 8-10 years before it starts to fail, for most people, it did it’s job. Now the quality of the application and the material used would factor into how well it held up, but on the whole, specially for us folks in the north east, I’d wager the few original cars still on the road owe a little of their longevity to their undercoating.

    Now I wouldn’t necessarily support undercoating a new restoration, specially if it was a concourse restoration, but if it was for a daily driver, I would recommend at least powder coating the pan and suspension components to help resist rust. Just paint wouldn’t last to long in this neck of the woods.

    Although this is anecdotal, my ’79 convertible, I’ve owned since ’83, was solid as a rock. Originally a California car, it didn’t have any undercoating. When I moved to Jersey in ’97 there wasn’t a spec of rust on it. Even though it saw snowy roads maybe a handful of times, it developed enough rust in the passenger side pan, that I needed to replace it in 2001. The ’79, along with my ’69 [another non-undercoated California car], no longer see salty roads. I now wait till after the third heavy spring rain to bring the cars back out on the roads.


    1. Hello, Jeffrey…Thank you for your viewpoint! I understand what you are saying. I knew full well that people, especially from the Northeast, might take issue with my philosophy. I’ve tried to talk myself out of thinking the way I do–then, I come full circle and have to rebuke myself for disbelieving 40 years of experience. LOL If undercoating prolonged the life of some cars–I am happy. But, I’m afraid that more succumbed to hidden rust than were saved. I’d certainly second what you say about powder coating. That is an effective manner for protecting metal. It does not seem to fracture or peel. It vigorously withstands the rock dings and scrapes and subsequent rust. It seems not to subtract from a car’s value. Some VWs had colors other than black on the undersides. Powder coating can handle that, too. jay

  6. My experiences with undercoating. Shortly after purchasing my 67 in the UK I thought, well, this weather will rust my beauty in no time-as it is quite damp in England. The car was outside all the time, no means of protection from the elements. Having previously used undercoating back in Florida on my 1949 Mercury and being an aircraft mechanic fairly well schooled in corrosion control I undertook to provide some rust security-in my thoughts anyway. At that time, for me, and most Yanks in the UK, J. C. Whitney was the provider of many things, as it seemed easier than trying to source up from the local economy. I ordered a gallon of undercoating and a car cover. The items eventually arrived, I put the car cover to work when not using the car. The undercoating was like roofing tar, very thick and unwieldy, especially in the cooler temperatures in England. So, I cut it with Kerosene and yes, sometimes a bit of gasoline, works wonders for thinning the stuff. I did the firewall, and area around master cylinder down on frame head with a putty knife, worked it on real well.L I remember doing some of this one night, it was about 30 degrees, and surprisingly I was quite comfortable doing the work. I did not undercoat much on the pan bottom at this time, as it was time consuming and difficult to access. After returning stateside, I moved underneath and used readily available spray cans on the bottom. Down through the years, I would reseal the bottom areas, where as Jay states, it would crack and large pieces flake off. My resealing over in patches over over eventually resulted in a fairly permanent coating on the pan. Rust repairs, I have had to repair a spot on both front wheel wells at the frame side-thus far, and that’s it. Just now I went out and checked the bottom, it is still good, including the battery area. I think the key for me was starting when it was still a relatively fresh vehicle. Also one must not forget, the factory Sealed/Undercoated the vehicles with WAX. Now, some 47 years later, I have tested the firewall area, alarmingly maybe, the gasoline smell is still there, sealed in-not strong but there. I still have the remnants of that original gallon of undercoating. Something else I used, Rust Oleum once upon a time had a red primer that was touted as using fish oil in it, I used many cans of that primer on scratches and bumps before undercoating-it was messy, took more than 24 hours to dry and much more in the cooler parts of the year in England.

    1. Hello, Quinn…Now, you really care about your cars! I’d have to put you into about a 1% of people who actually monitor the undersides of a vehicle! Wow! But, really, I believe that had you stuck to just cleaning and applying that Rustoleum you would have been ahead of the game–no globs of black stuff to flake and to gum up nuts and bolts, etc. I know exactly the product which you used. We used to live in the Northwest Amazon Basin in South America. I kept a can of the “original” red Rustoleum on hand all of the time. It stood up to the tropical rigors even on the interiors of our rain barrels! Not a pretty coating, but it worked.

      You remind me about the wax coating on the cars that were shipped overseas. At the port of entry or at dealerships, this wax was supposed to have been removed in make-ready departments. I am guessing that not all of the wax might have been removed before undercoating was accomplished. The undercoating certainly would not have adhered to such surfaces–nooks and crannies.

      I once ran the Red Baron–our trusted ’67 Beetle Sedan, through what might have been an acid. Anyway, it left a wide bared strip on the pan–devoid of paint. I got beneath the car, cleaned the entire passenger’s pan and coated with black Rustoleum. When it dried, it appeared as when the car was new. Years later, after I had sold the car, I was told that it was up for sale. I went to check on our old friend. In order to be sure that it was the same car, I looked at the pans. Yep–sure enough. It was the Baron himself. The paint on the passenger’s pan was still perfect! Thanks for some tips on undercarriage maintenance, Quinn!

  7. I receive feedback about this article even off-line. The following was sent to me by a acquaintance who was a trained VW Specialist, then had his own VW shop for something like 30 years. He still lives and works in the Northeast. Here’s what he had to say:

    “Hello Jay , I have to agree with your article. It was a money maker, pure and simple. Until it fully hardened it was fine, I suppose, but the expansion you speak of as well as road shocks, dings, rock damage,etc means the surface is full of openings that lead to the base metal and from there the undercoating is defeated. They talk about “cold flow”–ok, maybe…..for a while. I have seen a few VWs that didn’t have undercoating, because, after all, VW buyers were thrifty folks back then. They actually faired better in the salt/crap road environment than the undercoated ones. An unscientific opinion, I grant you, but I have seen the bottoms of a LOT of them over the years. All you can do is fix what’s left or look for another one.

    The undercoat is a purely Dealer implemented device, they don’t come from the factory like that !! One of the first jobs I did at the VW Dealership was (to) undercoat cars… I’ve lived with the guilt of it all my life,LOL, I hate that stuff too !! VWs look so nice with the body color in the wheel wells and the Black Pan, ahh, perfect….”

  8. [* WordPress Simple Firewall plugin marked this comment as “trash”. Reason: Failed GASP Bot Filter Test (checkbox) *]
    Thanks Jay for your coverage of undercoating! Very nicely done! My experience with n knowledge of Vera V, my mom’s 67, is as you described. She bought it new in Rapid City SD where the dealer applied undercoating for her. Fortunately for Vera V salt was not yet being applied to roads back then and when mom passed away in 94 the bug went to NM with my sister and now to me in AL where it’s garage kept so Vera V’s underbody is in pristine shape. But as you described the stuff comes off easily in places and in others it’s there and wants to stay there. We have very little snow in AL so salt application is minimal n and gets washed off right away if Vera V is taken out in it. Thanks again Jay!

    1. Hello, Ross…Thanks for reading my Article. I always am glad to hear a story like yours where the under-coating may have saved the Beetle’s pans! Mainly, it was a money-making effort on the part of the Dealerships. I have a ’68 Karmann Ghia which was under-coated , probably at a Dealership. It has provided me with opportunity to remove some of the stuff. I have friends at a local body shop. They showed me a sports car which had been under-coated. They were having to remove all of that stuff in order to be able to work effectively on the bottom of the car. This is going to cost the owner of the car dearly! I can tell that your Mother greatly enjoyed Vera V because she named her! What a wonderful inheritance you have–every time you and Vera V step out, I bet that your Mother is riding along in the passenger’s seat. Keep enjoying your ’67 Beetle! jay

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