Zinc chromate interior aircraft paint

Aluminium alloys used in aerospace have changed since the 1940s. Paints have changed too.  

Hello David - lots of cool info here! Thanks for sharing and have a nice day

Paweł

OK, let me add my two cents here. When I was in the Navy (up until 1996) and painting airplanes what was supposed to be done was to coat the bare metal with Alodine (a trade name, btw), spray on a thin coat of sealant (a rubberized material thinned to a water like consistency), followed by epoxy polyamide primer (looks exactly like green zinc chromate) followed by the topcoat color. In reality, nobody had time to do all that because Maintenance Control needed to fly that airplane yesterday or at most two hours ago. So we took shortcuts. The Alodine and sealant were skipped (unless it was the pre- or post-cruise corrosion control inspection). Bare metal was primed with epoxy polyamide primer and then the topcoat (another epoxy or sometimes polyurethane) was sprayed on. 

The only "Zinc Chromate" I ever saw came in a spray can and was used maybe once in a blue moon, often by folks who had nothing to do with the corrosion control shop. It turned an ugly shade of green after about two or three days and was not effective. Topcoats also came in spray cans and were used occasionally but they turned a kind of grayish brown color and looked awful. 

Trust me on the Maint. Control bit. I once painted an F-14 and within an hour (paint still wet) the AE's (electricians) were all over the top of the plane and so my nice gray paint job had black shoe prints all over it. Another time an A-6 I was working on was taken out of the hangar bay and flown with just the primer and no topcoat. Double the work for my shop since we had to remove all that primer, reprime it and paint it again when we got it back a week later. (Some of you might want to use these stories the next time you build an F-14A or A-6E)

This series of articles has lots of great info on colors. Pt. I is an overview of colors used. Pt. II is USAAF aircraft and colors by type. Pt. III is USN/USMC aircraft and colors by type

http://www.ipmsstockholm.org/magazine/2004/01/stuff_eng_interior_colours_us.htm

http://www.ipmsstockholm.org/magazine/2004/02/stuff_eng_interior_colours_us_part2.htm

http://www.ipmsstockholm.org/magazine/2004/05/stuff_eng_interior_colours_us_part3.htm

There's a lot ofpics of P-47s that have a yellow zinc in the well wells and green zinc in the cockpit and fusalage. I use MM forrest green instead of MM zinc chromate which I think looks too bright and florecent. Gary

high and the mighty

For years I have lain awake at night trying to decide if I was going to use zinc chromate green or zinc chromate yellow on the interiors of WW2 American aircraft, usually in exposed wheel wells but also sometimes in cockpits.  For a long time I didn't even know that there was a z.c. yellow, but I've giddily gone about using one or the other, often on a whim, where the model manufacturer didn't specify.

But now I have come by a delightful book entitled "The American Aircraft Factory in World War II" by Bill Yenne (you can find it on amazon.com) in which there are many color photos of workers--and a lot of cute Rosie the Riveters!--and ever one of them shows  z.c. yellow paint being used extensively.  Not a single photo shows z.c. green. And on top of that, the z.c. yellow is distinctly yellow, with just a hint of green in it.  So, while I will continue to use z.c. green when Im sure it's the right call, I'm stocking up on z.c. yellow (Tamiya makes a good one) and using that for the majority of my WW2 aircraft.  (Don't get me started on the bronze green controversy!).

 

The Bronze Green is actually the color used in B-17 Cockpits, I know because I volunteer at the B-17E 41-2595 DesertRat Restoration Project and the cockpit has it's original paint, and it's the on the yoke column and throttle quadrant. And that color is also listed in the blueprints as the color for the cockpit interior.

I recall not too many years back an article in a warbird magazine where someone was restoring a full scale AT-6 back to airworthy status.  The aim was to make this warbird totally authentic, down to the proper radios and so on.  A variety of N.O.S. parts was obtained for this aircraft from around the country, and not a single one of the parts in the photos matched the exact color of any other part.  We are talking about the same aircraft, built by the same manufacturer, and the parts from the production line were rather different.  Suffice to say, depending on what you are building, it is even possible that one aircraft could have had different colors on different parts, for example within the same cockpit there could be variations on different parts.  I guess the real answer here is "there is no one right answer".  

I took it down.

Outstanding set of photos.  What jumped out at me was the guys spaying without any protective gear.  Ahhh.... The good old days when we didn't know what was killing us.

I came across these photos in the Life archives of ZC application on the P-40 production line in 1941

Thank you Life.

The reason zinc chromate is seeing much less use today is because as a carcinogen the requirements for using it have pretty stiff epa rules.  So today the etches, like Alodyne are more popular.

Mij

The testors basic enamel line (1/4 oz square bottles) has a fairly yellow zinc chromate. The product number is 1184.

Here's an example of the Testors yellow zinc chromate in the 1/4 oz. bottle in use on my RF-101B Voodoo:

I found this in the article:

There is evidence that such variety of shades occurred in the manufacturing practice of US aircraft factories. Where sufficient colour evidence is available, it is possible to find all three colours used on the same aircraft - for example, the yellowish raw colour in the wheel wells, the apple green tones in the gun bays, and the darker green in the cockpit.

Just to add to Tarnship's comments about green zinc chromate as a coating.

We use modern day zinc chromate, sometimes just zinc and sometime yellow zinc. Yellow or green zinc has a higher resistance to corrosion.

Zinc is usually plated on via a chemical etch.

Chromate can be sprayed on, or etched on a part that is already zinc plated.  I had always assumed that the parts on an aircraft were etched but I guess they were sprayed. I had to do some research on this as I didn't even know that it could be sprayed.  It's pretty toxic stuff, not sure if it is still sprayed today as the parts we order are a chemical etch.

I hit enter too soon, cutting my post short

There has been a lot written over the years about when to use yellow or green zinc chromate "color", and it seems that one thing gets left out a lot

Zinc Chromate is not a color on real aircraft, it is/was a coating

the first coat right out of the can was the Yellow Zinc Chromate coating, the color was in therefrom the factory that made the coating

the second coat of Zinc Chromate was a mixture of the Yellow ZC, tinted with Black (or Red) to show where the second coat had been applied (which was not the entire aircraft), this was tinted at the site, so could vary quite a bit from site to site, or day to day

any "interior color" would have been applied over the Yellow or Green (or Salmon) ZC as a color topcoat,,,,a "scratch test down to bare metal" would show two or three colors, but never just one

There was a detailed thread on this subject here awhile back.  I seem to recall there were many shades of yellow/green used, depending on the supplies on hand at the time.

Why not do what I do?  Use either one, depending on how it fits the overall color scheme of the aircraft.  Or use 'em both on the same model!  Right now, I'm building a P-51D, with yellowish green in the engine compartment and greenish yellow in the cockpit!  It looks fine and adds interest.

A few years ago I had a chance to inspect a restored B-17 closely.  The insides and wheel wells were all green zinc chromate.

Oh my, big ball of wax here!

I'm not an expert on ANY aircraft from WWII, but I've seen alot of pics of planes from this era, both factory and in operational use. And I understand that sometimes colors like zinch chromate green and yellow was used alot on most aircraft. The yellow zinc was a primer, so it will be seen in alot of factory pics. 

 I dont know where I'm really going with this though other than saying, I preffer using interior green instead of green zinc, mainly because of scale effect. Those 2 colors look totally differant from a real airplane vs a model of the same plane. I like using a variety of colors inside one model, interior green, green zinc, and dull dark green (aka bronze green) (MM euro dark green is the best for matching this) to give the impression that differant components came from differant places, as they often did.

I dont know, to each his own I guess.

Yes ZC yellow was used extensively on US aircraft in just about any interior location you can think of... except cockpits.

This site has a good breakdown by aircraft type of interior colors used.

http://www.ipmsstockholm.org/magazine/2004/01/stuff_eng_interior_colours_us.htm

It makes complete sense that most of the pictures in that book would show ZC Yellow, especially if it shows parts being painted in primer for the first time

The Black was only mixed into the Zinc Chromate coating to show painters where a second coat had been applied, as in wheel wells and such