GM Heritage Center Documentation / Underbody color

[DavidS]

I have a clearer idea on what you are saying now Mark when you wrote "Your lucky if the center area under a Norwood car got anything more than a light dusting of primer".    Step 4 gray primer was not a thorough application of primer.  Therefore when we look at the underside we are looking at whatever was put on in either Step 1 or Step 2.

[Oaklyss]

My floors have lots of overspray. Where overspray was knocked off, its black under:

[DavidS]

My floors have lots of overspray. Where overspray was knocked off, its black under:

It's black primer, correct?

Is your car a Norwood car?  What's the build date?

My car is a 01B, 2nd week of Jan 1969.

[Oaklyss]

It's whatever GM put there

O4A LA car. Original paint, the overspray is factory applied.

[DavidS]

It's whatever GM put there

HA!!!  

At first I thought that it's "Four corrosion resistant primers, specially formulated" and "hand sprayed".  But you don't see black all over the rest of the body.

However, when I read the rest of step 2 it states "Lower areas considered especially vulnerable are coated with another rust inhibiting compound."

So my best guess is that the black areas are "rust inhibiting compound".

[DavidS]

Maybe it's "hammerite" which came out in 1962 ?

[ChrisM]

Maybe it's "hammerite" which came out in 1962 ?

Wow!  You may be on to something.  I googled that.  Hammerite is zinc phosphate based. 

[NoYenko]

Many years ago we used GM restoration paint in Gal. cans for Corvette restorations. Currant # 1050104 available from dealer or other suppliers. I don't know if it still matches the paint from 30 years ago.
Maybe someone has recently used it and can give feed back.
George

[DavidS]

At a place I used to work, we did material analysis with machines like this one:
http://www.helmut-fischer.de/independent/31/XAN_en.asp
And this one:
http://www.helmut-fischer.de/independent/31/XUV773_en.asp
If I had samples of each and I could get a few favors at Fischer, a comparison could be made between black samples from a couple cars and Hammerite.

….or…..maybe I am nuts and should just go 30% gloss black and call it a day.

[bcmiller]

David, if you have connections, I think that would be a worthwhile project.  I don't have a survivor car, but hopefully others would agree to submit samples for analysis.

[DavidS]

I have connections and used to work at Fischer.  I would have to talk to my former boss and see if he would agree to some testing.  I don't think it would be a big deal for him though.

However, if JohnZ or anyone else knows what "another rust inhibiting compound" actually is, this might be resolved quickly.

[68Zproject]

Just to clarify, what color is the primer on the underside?

 

Black paint, or black phosphate coating?

Or whatever it's called.  The question for my LOS car would be; what color was underneath it before the exterior paints were applied?  And what was the color of the primer that was sprayed that "oversprayed" onto the bottom of the car?  From my reading, there should be a lot more of this on LOS cars as they were higher off the ground when sprayed.

[68camaroz28]

I was just under a 68 Z/28 survivor this week observing things for our restoration and the only color other than the body overspray underneath was black. Our Oct. 69 Norwood car is a TN never undercoated Camaro and other than the Lemans Blue overspray it's all black. I honestly do not remember working on a car with a gray bottom but that does not mean they do not exist as I'm sure they do somewhere.

[JohnZ]

I would have thought the blackout paint on the rockers would have been painted after the front end was on but this picture shows a masked line over the Lemans blue on an area covered by the fender normally.

The body was painted by Fisher, including the rocker blackout, in their Paint Shop; the front sheet metal was painted separately by Chevrolet, in their Paint Shop, including the continuation of the rocker blackout on the lower fender, before the front sheet metal was assembled to the body, as noted in the Assembly Manual in the Z21 and Z22 sections.

[68Zproject]

So John, do you know what the color of the bottom of the Camaro should be and what was this color made of?  And what was the color of the primer that was sprayed by hand that overspryed under the car?  Was this color more pronounced on LOS cars vs. NOR cars because of the height on the lines?