Original Black Primer Underside of Body 69 Z/28's

[Bryan302]

What is the tough black primer / sealer being found on underside of Norwood body floor pans, especially on Z/28's?  It appears to be extremely tough and is applied directly to bare metal.  The grey primer / sealer or red oxide primer is applied over this, and all underside over spray.  What is this black primer that the factory used?  Can it be replicated and acquired in modern day body shop supplies?  What has been found to be the average coverage of this black primer on the underside floor pans? 

Thanks,
Bryan

[BillOhio]

There's a good thread on this but I can't find the link I thought I saved. I think this is Gary's car. Mine was similar. Had grey in tunnel and foot board areas. I believe black was over the grey. I used sikkens rally black over ppg epoxy primer on my car. Sikkens is pricey but excellent product.

[Mark]

The black is a phosphate coating, any other colors, greys, blacks reds etc are primers sprayed on in the paint booths

[69Z28-RS]

There's a good thread on this but I can't find the link I thought I saved. I think this is Gary's car. Mine was similar. Had grey in tunnel and foot board areas. I believe black was over the grey. I used sikkens rally black over ppg epoxy primer on my car. Sikkens is pricey but excellent product.

Nope, that one is not mine, although mine is similar.   That one shows more area with the 'black still exposed'.  My car's floor shows the black in the tunnel and 'high areas', but other primers and oversprays in the lower areas...   The gray primer in the trans tunnel portion is similar to mine, which makes me believe they 'primed the firewall - and maybe more of the car - gray before painting...   I also have some 'red oxide/brown' primer regions under the car, apparently from overspray when the car was painted?

[69Z28-RS]

The black is a phosphate coating, any other colors, greys, blacks reds etc are primers sprayed on in the paint booths

Mark.   That's the first time I've heard phosphate mentioned for that..  Can you elaborate?   was the entire body subjected to a phosphating process?  or just some panels (like the floor) prior to assembly of the panels into the body? or?    Any details you can provide based on fact, or conjecture based on evidences would be greatly appreciated.

[cook_dw]

There's a good thread on this but I can't find the link I thought I saved. I think this is Gary's car. Mine was similar. Had grey in tunnel and foot board areas. I believe black was over the grey. I used sikkens rally black over ppg epoxy primer on my car. Sikkens is pricey but excellent product.

I believe that is George's car (NoYenko).

http://www.camaros.org/forum/index.php?topic=9029.0

[JohnZ]

The black is a phosphate coating, any other colors, greys, blacks reds etc are primers sprayed on in the paint booths

Mark.   That's the first time I've heard phosphate mentioned for that..  Can you elaborate?   was the entire body subjected to a phosphating process?  or just some panels (like the floor) prior to assembly of the panels into the body? or?    Any details you can provide based on fact, or conjecture based on evidences would be greatly appreciated.

The phosphate systems (both of them - Fisher's and Chevrolet's) are covered in some detail in the "First Generation Camaro Assembly Process" paper on this site, at:

http://www.camaros.org/assemblyprocess.shtml#fisher

Here's an excerpt - go to the paper to read the details:

<<Fisher Body - Paint Shop Operations
The Paint Shop is broken down into phosphate, prime, sealing, and color departments; the body was suspended from an overhead conveyor with hooks at the firewall and at the ends of the rear frame rails through the phosphate system, and was transferred to a steel carrying truck before the prime system that carried it through the rest of the Paint Shop and through the Trim Shop.
Phosphate System: The raw body shell passed through a seven-stage phosphate system, where it went through a series of enclosed high-pressure hot spray stages where it was washed to remove all the oils and debris from stamping, welding, brazing, soldering, and grinding operations, then the body was coated with a hot iron phosphate solution which "etched" the metal and provided "teeth" for paint adhesion. The final stage was a de-ionized hot water rinse and blow-off, followed by a drying oven on the way to the prime booth.>>

[69Z28-RS]

John,

Thank you very much..

I'd read your description previously, but I guess I didn't associate that phosphating process described with the 'hard black' coating on the bottom of my floor... It's amazing that it lasted so well so long if that's what it is..

Was the full floor bottom 'primed' in the priming booth?  or only the top and sides...?   Large portions of my floor only show the 'black' (apparently phosphate coating from what you guys are explaining to me)..

Gary

[Bryan302]

Thanks Bill, Mark, and John.  This was exactly what I was looking for.  Those sources for modern brands of primers and the steps of application.  Lately, I have noticed several restored Z's with mostly grey sealer on the under side.  Of course, they would be black down the firewall, and starting under the bottom to roughly the rear of the bell housing, and then grey sealer from there on back, and then the body color over spray on the sides.  John, Was there any differences in "the way the plant did it" in any other time period, or was Bill and Gary's example "the standard" all the way through production? 

Thanks,
Bryan

[Mark]

Anything under the car is overspray of either the primer used, body color, sill or firewall blackout.  The bottom of the car was never purposely sprayed with either primer or body color paint.  At least at Norwood since the body was  sitting on a truck about 18: off the floor, there was no way to physically get under the body to spray anything after the phosphating process was complete.  LA held the bodies higher on suspended carriers so they are more likely to have more overspray, but again it was not done on purpose.

[69Z28-RS]

The majority of the underside of my car is 'black/dark gray'.. (the phosphate apparently).. which explains how touch it is.
I also have some 'oversprays' of  red oxide/brown (primer?), and gray (sealer?), and orange (topcoat color), as well as a little black (rocker blackout)...  I think this corresponds perfectly to what John Z wrote in his paper re " First Generation Camaro Assembly Process", ie...

"The Paint Shop is broken down into phosphate, prime, sealing, and color departments;"...

I'm attempting to assist Bryan302 in his restoration, and I think the only part of this we have to 'simulate' is the phosphating 'black/darkgray' first step.   Does anyone have any suggestions for how to best perform that step??

[BillOhio]

Gary, I know its not primer, but the sikkens rally black I used is low gloss like the firewall and will be a lot tougher. I used it as the phosphate coat. I wasn't crazy about leaving a primer on the bottom and not top coat it. Ppg makes epoxy in several colors including light and dark grey that I think would be close in color

[69Z28-RS]

Gary, I know its not primer, but the sikkens rally black I used is low gloss like the firewall and will be a lot tougher. I used it as the phosphate coat. I wasn't crazy about leaving a primer on the bottom and not top coat it. Ppg makes epoxy in several colors including light and dark grey that I think would be close in color

Bill,  Thanks for your suggestions; I also suspect that preparing the bottom of the car and using a hardened paint (epoxy or urethane), mixed to approximate the color and gloss levels would best serve as that 'first protective coating' of the floor.  I used PPG epoxy primer on my Nomad floor to approximate the factory's brown/redoxide primer used in the 50's..