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FS Green Zinc Chromate


smotti

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What is your intended use for that color, if I may ask? 

 

To add to what's been said:  Zinc Chromate is yellow in  color in it's untinted state.  If you're wondering about zinc chromate green, that color is not widely used a lot on aircraft that I've been exposed to and does not have a MIL-SPEC (MIL-STD-595/ SAE-AMS-STD-595) equivalent.  I can't even find a close proximate in the 595b fan deck I have (yes, I know it's not current..doesn't matter for purposes of this discussion).  FS34151 Interior Green is the modern day equivalent of what used to be called tinted zinc chromate.  To get tinted zinc chromate, you add black to the yellow zinc chromate in a certain ratio (which I have forgotten).  I no longer buy  Model Master FS34151 as I had three bottles of it at different times in the past and each bottle was a different shade of green.  Now I create my own, the way I've outlined above except I add black to the yellow zinc until it looks right.  I don't try and match the FS color chart.  For what I build (mostly WWII) the FS system wasn't even around then and manufacturer's mixed their own anyway.  As far as WWII US aircraft are concerned, close is good enough.

 

If you mix too much black into the yellow zinc, you'll wind up with olive drab...not close.

 

Modern day stuff is another story.  You may find such a shade on some military aircraft in differing spots.  I can't think of one offhand but with the environmental friendly paints being developed, zinc is not being used as much as it was in the past (it is a health hazard).  That shade of green may be used but it won't be called zinc chromate green.  As a "fur-instance", the UH-60M's we converted for FMS at the Sikorsky plant I worked at for a few years (until it closed), came to us partially in helo-drab (don't know the FS for that but it has one), partially in a very gaudy, 1950's kitchen green semi-gloss primer and then we added a water-based greenish-grey primer to our modifications....  This was, of course, prior to it going into the paint booth and getting painted to the customers specifications.

 

 

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The recipe  of zc was about the ingredients, not about the color of it. Every Manufacture of airplanes had there own preferences. So the color depends on what your building   

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13 hours ago, Theo said:

The recipe  of zc was about the ingredients, not about the color of it. Every Manufacture of airplanes had there own preferences. So the color depends on what your building   

 

I disagree. 

 

The "recipe" of zinc chromate was spelled out in AN-TT-P-656.  The natural color of zinc chromate primer is yellow (for lack of the exact term for the color).  Jennings has already said that the coloration (untinted zinc chromate) was based on its chemical makeup, not because pigmentation was added.  What's being discussed is the green color of tinted zinc chromate versus the MM color "zinc chromate green".  I've already stated that the color of tinted zinc chromate varied with each manufacturer.

 

Per Boeing B-17F E&R manual (T.O. 01-20EF-02 page 439) and B-17G E&R Manual (T.O. 01-20EG-02, page 422)

 

"Wherever carbon black tinted primer is specified, it shall consist of or be equivalent to, 8 ounces of carbon black tinting paste (Fuller's No. 790 or equivalent) per gallon of zinc chromate primer."  Carbon black tinted primer = interior green, Boeing style.

 

Per Northrop P-61 E&R Manual:

 

"All exposed interior surfaces of the gunner's, pilot's and radio operator's compartments shall be finished with Northrop Cockpit Green (12 oz. of black camouflage enamel AAF 14109 to one gallon of zinc chromate primer Spec.No. AN-TT-P-656)".  Interior green, Northrop style.

 

P-51D E&R manual (AN 01-60JE-2, pages 403-406):

 

Various structural members:  "zinc chromate primer per AN-TT-P-656". 

"Interior green "spec no. E-7 flat black to be used."  Interior green, North American style.

Edited by Juggernut
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Juggernut,
I bought the Eduard colored photo etched set for the TBD-1 Devastator from GWH.
Two pieces are painted a light green tone, which I thought was the Green Zinc Chromate.
As here in Brazil we do not have suppliers for Model Master inks, I wanted the Federal Standard code to get an equivalent of another brand.
However, if I understood the considerations the correct color for the interior of this model would be the Interior Green FS 34151.
Or could it be the Yellow Green (Tamiya XF-4)?
Thank you all for the comments.

Sandro

 

 

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7 hours ago, smotti said:

Juggernut,
I bought the Eduard colored photo etched set for the TBD-1 Devastator from GWH.
Two pieces are painted a light green tone, which I thought was the Green Zinc Chromate.
As here in Brazil we do not have suppliers for Model Master inks, I wanted the Federal Standard code to get an equivalent of another brand.
However, if I understood the considerations the correct color for the interior of this model would be the Interior Green FS 34151.
Or could it be the Yellow Green (Tamiya XF-4)?
Thank you all for the comments.

Sandro

 

 

Sandro,

 

Given that the Federal Standard code did not exist until well after WWII (circa 1950's),

trying to ascertain what Green tinted Zinc Chromate was used by Douglas (paints mostly

Fullers manufacture as I understand it) and  Post WWII FS colours is a bit like the proverbial

"Square Peg in a Round Hole". The two do not match.

The other issue you have is, are you building a Pre 1940 or a post 1940 aircraft?

Pre 1940 TBD's most likely would be "Aluminum Lacquer" interiors as opposed to having Green tinted Zinc

Chromate.

The M&R manual for Curtiss P40 M/N's specifies 100 gallons of Zinc Chromate Primer (AN-TT-P-656)

and then between 0.1 - 0.4 lbs Lamp Black (TT-L-71) or 0.1 - 0.4 lbs Carbon Black (AN-TT-C-121) with between

1-3 lbs of a Whitening agent and 8-10 lbs of MgSi.

The colours depending on mixing will give you a wide spectrum of Yellow Green "Cockpit Green" as cited in the

finishing section.

I tried mixing some for a P40K build and note the colours with differing amount of Zinc Chromate/Black

384a6341-d6af-411a-b9e8-3b0ab9756a85.jpg

 

Regards

 

Alan

 

 

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Hi Sandro,

 

You simplified the conversation as soon as you mentioned the TBD...

 

First, pre-war zinc chromate primer was different from post-war primer.  In the 1930s manufacturers didn't add a quantity of zinc chromate to a bunch of other chemicals; they added a minimum quantity of zinc oxide and a minimum quantity of chrome oxide to those other chemicals.  The suspension resulted in a zinc chromate primer.  Since chrome oxide was more expensive, manufacturers tended to use less of it.  The resulting primer was always yellow, but the color varied greatly with the percentages of the two pigments used.

 

The original idea was to apply two coats of zinc chromate primer to the aircraft interior, then a finish coat of aluminum pigment suspended in clear lacquer.  In the mid-1930s Wright Field advised Northrop that the manufacturer could save time and money by suspending the aluminum pigment in the second coat of primer, then skipping the finish coat.  The result was "aluminized zinc chromate."  Northrop gave the recommendation a try, then wrote back that the result was actually green!  Wright Field gave a sure-what-ever response and aluminized zinc chromate came into use.  Since Northrop was a Douglas company at the time, aluminized zinc chromate became an industry standard seen on several Douglas aircraft.

 

But this bright green must have been too bright for the Air Corps, since most standards added a tinting black to the formula - the result was a color called Yellow Green.

 

TBDs originally used aluminized lacquer as a cockpit finish coat, but TBD crews objected that the reflections interfered with night flying.  They created their own mix of black and zinc chromate primer that they felt was close enough to the very dark Bronze Green enamel that was then coming into style.  They provided no formula, and there are no known surviving samples, so you get to pick any dark olive green that suits your tastes.

 

The evolution of wartime green zinc chromate is a completely different story that won't fit here - but there are more options there when the time comes...

 

Cheers,

 

 

Dana

Edited by Dana Bell
word left out
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Even today , common aircraft primers (which look alot like ZC) are sensetive to mix ratios and vary widely.

There's a range they need to shoot for but since they are just primers, the actual shade is not important

as they're not considered cosmetic. I think it's safe to assume the same was true back then too.

 

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