5/72 240z and undercoating

[jonathanrussell]

I decided to create a new topic to continue the discussion regarding factory undercoating and whether primer / paint was used or not.

I understand and it makes sense that the factory may have done different things over the years with regard to undercoating so all I can really present and comment on is my 5/72 240z.

I would really like to see what @Carl Beck, @26th-Z, @bluezand others think about what I am seeing with my car, relative to what has been written and thought about the topic over the years.

My car is a 5/72 240z. It has original 918 orange paint that is in excellent condition. The car shows approximately 24k miles and in every way that I can think of reflects that number.

I am refreshing the car but am preserving the original exterior paint and pristine original interior.

The car was stored for decades after having a blown head gasket. This probably saved the car and preserved it.

I am refreshing everything else- engine, everything under the unibody, rubber, etc. I have refinished the engine bay and front unibody that the fenders, hood, valence, etc mount to.

I am currently refinishing the floors and underbody behind the floors.

My car has what I believe to be factory tar undercoating top coated with 918 orange (though thinly top coated). It is what 26th-Z describes as a "thicker textured paint finish". 

In my opinion this is a typical tar undercoating with lots of texture, top coated with the same paint used on the exterior- in my case 918 orange. 

My eyes and experience with stripping the undercoating tell me that what is beneath the tar undercoating is nothing but galvanized metal. I can remove the galvanization mechanically or with acid. This coating, to me, doesn't behave like a primer or paint and doesn't look like it either to my eye. It won't come off with aircraft paint remover. It only comes off with a wire wheel or acid.

Here are some photos that I hope show what I am seeing.

 

This is the floor before stripping. I used a heat gun and a putty knife to remove the "painted tar undercoating".

 

 

 

The photo below shows what the painted undercoating looks like when removed. The painted side is painted. The tar undercoating portion is what I know tar undercoating to be. And, there is no primer or paint on the underside of the tar undercoating (the black side). It is just black tar undercoating.

 

 

 

The photo below, to me, raises the most questions. To my eye, the left side shows what I now see all over my floors and tunnel- a mixture of bare metal and galvanized metal. Clearly the transmission brace is bare metal. The tunnel surrounding, to me, shows a galvanized / electroplated sort of coating. To me, this doesn't look like and it doesn't behave like a primer. Aircraft paint remover does nothing to it. The only way to remove it and make it look like the transmission braces is to either wire wheel it or treat it with acid. Am I seeing this wrong? Is it really some milky looking super thin primer?

The right side shows the painted undercoating. What I see where the undercoating ends and metal begins is painted tar undercoating where my tool has, at the edges, scraped away some of the paint leaving only black tar undercoating.

 

 

 

So, I am interested in what Carl, 26tth-z, bluez, and others think. Please let me know if I am wrong about what I am seeing. I truly want to know, and I want others to know, how at least the 1972 (or maybe just the 5/72) cars were delivered. 

I also have a 10/71 1972 240z in Silver. It is not at all close to the condition of this car....but have seen the same where I have removed some painted undercoating in the past.....though all of it has now been refinished to preserve the metal. 

 

Thanks all.

J 

 

 

Edited October 5, 2022 by jonathanrussell

[26th-Z]

We're talking about two different things.

To me, this is undercoating

[26th-Z]

This, to me, is a factory underside finish.

[jonathanrussell]

But isn't the "factory underside finish" just tar undercoating with a coat of paint on top?

[Patcon]

That is what it appears like to me

[Namerow]

Undercoatings of the 1970's were variously described as, 'oil', 'tar', 'asphalt', or 'wax' ('paraffin' if you're a Brit).  If you investigate further, you'll find that each of these terms is somewhat generic and not really precise from any chemical engineering perspective.  For automotive purposes, 'oil' meant sprayed-on and could be anything from heavyweight used crankcase oil to purpose-blended lightweight stuff.  'Tar' meant 'thicker but still sprayed-on', while 'asphalt' translated to 'thick and usually brushed-on'.  'Wax' was typically interpreted to be 'less oily', sprayed-applied, and suitable for internal body cavities like doors and rockers (Zeibart and Wax-oyl were two of the better-known wax-type aftermarket undercoating treatments).  

It's hard to say what kind of material Nissan used for the underside of the Z's.  Obviously, it bonded well to the metal and skinned over nicely so that the paint spray adhered (for fifty years).  I wonder, though, whether Nissan's objective may have been sound deadening as much as corrosion protection.

Like many others, I remember using brush-on undercoating on the underside of my first Z after the first rust blooms appeared.  I think that we all hoped it would 'seal off' the underside of the car from further exposure to winter road de-icing salt.  It certainly looked the part.  Alas, it didn't work.

[bluez]

On 10/4/2022 at 10:10 PM, jonathanrussell said:

I decided to create a new topic to continue the discussion regarding factory undercoating and whether primer / paint was used or not.

I understand and it makes sense that the factory may have done different things over the years with regard to undercoating so all I can really present and comment on is my 5/72 240z.

I would really like to see what @Carl Beck, @26th-Z, @bluezand others think about what I am seeing with my car, relative to what has been written and thought about the topic over the years.

My car is a 5/72 240z. It has original 918 orange paint that is in excellent condition. The car shows approximately 24k miles and in every way that I can think of reflects that number.

I am refreshing the car but am preserving the original exterior paint and pristine original interior.

The car was stored for decades after having a blown head gasket. This probably saved the car and preserved it.

I am refreshing everything else- engine, everything under the unibody, rubber, etc. I have refinished the engine bay and front unibody that the fenders, hood, valence, etc mount to.

I am currently refinishing the floors and underbody behind the floors.

My car has what I believe to be factory tar undercoating top coated with 918 orange (though thinly top coated). It is what 26th-Z describes as a "thicker textured paint finish". 

In my opinion this is a typical tar undercoating with lots of texture, top coated with the same paint used on the exterior- in my case 918 orange. 

My eyes and experience with stripping the undercoating tell me that what is beneath the tar undercoating is nothing but galvanized metal. I can remove the galvanization mechanically or with acid. This coating, to me, doesn't behave like a primer or paint and doesn't look like it either to my eye. It won't come off with aircraft paint remover. It only comes off with a wire wheel or acid.

Here are some photos that I hope show what I am seeing.

 

This is the floor before stripping. I used a heat gun and a putty knife to remove the "painted tar undercoating".

 

 

 

The photo below shows what the painted undercoating looks like when removed. The painted side is painted. The tar undercoating portion is what I know tar undercoating to be. And, there is no primer or paint on the underside of the tar undercoating (the black side). It is just black tar undercoating.

 

 

 

The photo below, to me, raises the most questions. To my eye, the left side shows what I now see all over my floors and tunnel- a mixture of bare metal and galvanized metal. Clearly the transmission brace is bare metal. The tunnel surrounding, to me, shows a galvanized / electroplated sort of coating. To me, this doesn't look like and it doesn't behave like a primer. Aircraft paint remover does nothing to it. The only way to remove it and make it look like the transmission braces is to either wire wheel it or treat it with acid. Am I seeing this wrong? Is it really some milky looking super thin primer?

The right side shows the painted undercoating. What I see where the undercoating ends and metal begins is painted tar undercoating where my tool has, at the edges, scraped away some of the paint leaving only black tar undercoating.

 

 

 

So, I am interested in what Carl, 26tth-z, bluez, and others think. Please let me know if I am wrong about what I am seeing. I truly want to know, and I want others to know, how at least the 1972 (or maybe just the 5/72) cars were delivered. 

I also have a 10/71 1972 240z in Silver. It is not at all close to the condition of this car....but have seen the same where I have removed some painted undercoating in the past.....though all of it has now been refinished to preserve the metal. 

 

Thanks all.

J 

 

 

Looking at your pics, have to agree.. Looks like galvanized metal, with tar, and paint.  My 12/70 just has paint, with undercoating sprayed on top. See pic. Real pain to remove without ruining paint. So later cars had “improvements”.