C3 birdcage color. Green vs. black

[Mike E.]

I know that on midyears that varied A.O. Smith vs. St. Louis bodies. On 70-72 cars, why are some green zinc chromate and others black? I probably should know this, but I confess my ignorance. Fill me in, please.

[Patrick H.]

Re: C3 birdcage color. Green vs. black

Which locations with regard to color? All of the cage, or...?

The painting process changed through the years, though I don't think it really did in the 70-72 years.

[Mike E.]

Re: C3 birdcage color. Green vs. black

Not much response here, so let me add some pictures. Patrick, per your question; all of the cage.
Here are pictures of unmolested cars:
71 in the 7000 vin range:
birdcage (2).jpg birdcage.jpg

From 71 in 12500 range:
birdcage (3).jpg birdcage (1).jpg
From 72 in the 8000 range:
Body mount (3).jpg

[Patrick H.]

Re: C3 birdcage color. Green vs. black

Interesting. One wonders if GM was testing a different paint at one point?

[Mark F.]

Re: C3 birdcage color. Green vs. black

Interesting. One wonders if GM was testing a different paint at one point?

Hi Mike and Patrick,

Yep...or, maybe the GM engineering spec did not specify what color the birdcage paint (coating) had to be...the spec may have only indicated what minimum concentration of zinc chromate (ZnCrO4) was required; along with requirements about how well it would cover and protect with a single-coat spray?

Speculation on my part, but based on my employment history with both Ford and PPG, I would also guess they would not want to potentially be held hostage by only having one supplier for something that was used on every Corvette unit produced. Don't know for sure, but other GM models probably had some parts painted (or coated) with zinc chromate, too. Different suppliers may have chosen to use more black pigments (if the the green we are used to seeing was not a GM requirement)...

The attached link is aircraft-related, but I think it provides interesting perspective regarding the history of what color(s) zinc chromate coatings could be. As they say in the link, Because Zinc Chromate is all about corrosion protection, the precise coloring of it is and has not been considered as important as the chemical composition.

enjoy...

http://www.colorserver.net/history/history-zinc-chromate.htm

[Mike E.]

Re: C3 birdcage color. Green vs. black

Mark,
Thanks for your input. I know that the two different C2 body plants used different colors, but never considered the fact that GM would likely have specified them identically, with color being incidental. I have seen no pattern in 70-72. They apparently used whatever was in the drum closest to the storeroom door.

[Owen L.]

Re: C3 birdcage color. Green vs. black

My May '72, #20,2xx has black. If you're collecting data to see any trends.

[Mark F.]

Re: C3 birdcage color. Green vs. black

I know that on midyears that varied A.O. Smith vs. St. Louis bodies. On 70-72 cars, why are some green zinc chromate and others black? I probably should know this, but I confess my ignorance. Fill me in, please.

Interesting. One wonders if GM was testing a different paint at one point?

My May '72, #20,2xx has black. If you're collecting data to see any trends.

Mornin' Guys,

I ginned up a spreadsheet for tracking these Birdcage colors by year and body style if any of you are interested in that.
It is in Excel, which is not easily pasted into TDB posts...so, the attached PDF shows you what it looks like.

I'll be happy to send it (email it) to any of you who might want to keep track of this(?)
I don't know if the Coupe vs Conv. is important to you? I can take that out if that's not needed.
Let me know if you want any other modifications - and/or if you think a survey/tracking of this is not really worth the effort

1970 to 1972 Corvette Birdcage Zinc Chromate Color Observations.pdf

[Terry M.]

Re: C3 birdcage color. Green vs. black

Mark

I suggest you spread your sheet forward to 1968, and I do think coupe v convertible is important because we might find there is a color difference for those different body styles.

That said:
1970 Coupe #2161 is green.
1969 coupe #13,586 is green

[Mark F.]

Re: C3 birdcage color. Green vs. black

Mark - I suggest you spread your sheet forward to 1968, and I do think coupe v convertible is important because we might find there is a color difference for those different body styles. That said: 1970 Coupe #2161 is green. 1969 coupe #13,586 is green

Hi Terry,

Like this?
I tweaked it a little to keep track of counts and ratios of Green to Black...
lemme know if you want any other changes...

1968 to 1972 Corvette Birdcage Zinc Chromate Color Observations.pdf

[Dan A.]

Re: C3 birdcage color. Green vs. black

My early built 72 (August) also has the green paint.

[Mark F.]

Re: C3 birdcage color. Green vs. black

Hi Dan,

Not sure if this spreadsheet has wings or not, but if you're willing to share, for quantification purposes the following would be needed to make the output worthwhile:

1. VIN Range (Last 5): We need the 1st three digits to identify potential transitions (###); the last 2 digits are not required, unless you care to share them - if not, just enter "##" as the last 2
2. Coupe or Convertible?
3. Green or Black (as you have already submitted)

[Dan A.]

[Terry M.]

Re: C3 birdcage color. Green vs. black

Hi Dan,

Not sure if this spreadsheet has wings or not, but if you're willing to share, for quantification purposes the following would be needed to make the output worthwhile:

1. VIN Range (Last 5): We need the 1st three digits to identify potential transitions (###); the last 2 digits are not required, unless you care to share them - if not, just enter "##" as the last 2
2. Coupe or Convertible?
3. Green or Black (as you have already submitted)

Oh I think it will have wings, but let's see where it goes.

[Owen L.]

Re: C3 birdcage color. Green vs. black

Hi Dan,

Not sure if this spreadsheet has wings or not, but if you're willing to share, for quantification purposes the following would be needed to make the output worthwhile:

1. VIN Range (Last 5): We need the 1st three digits to identify potential transitions (###); the last 2 digits are not required, unless you care to share them - if not, just enter "##" as the last 2
2. Coupe or Convertible?
3. Green or Black (as you have already submitted)

My May '72, #20,2xx has black. If you're collecting data to see any trends.

To add the details required: VIN 20284, coupe, black birdcage