Hello everyone;
I’ve a couple of questions about color. I’m new to modeling and want to know what color zinc chromate is. I’ve seen it as mostly green and I’ve seen it as mostly yellow. Both were made by Testors. I’d like to know which would be used for the Accurate Miniatures “Doolittles Raider” B-25 Mitchell 1:48? Also is there a “blue” zinc chromate? Any info would be helpful.
Thanks,
Steve Gorder
The green shade is what you want. Zinc Chromate green was commonly used for interiors while Zince Chromate yellow was more often found in landing gear bays. Moseld Master has an acylic Zinc Chromate green that is pretty good seen here on a B-26B Marauder…
and here is the yellow zinc chromate (Testors) in a landing gear bay…
First and foremost, [#welcome]
Next, both are chromates. They are corrosive preventive primers. In reality, both colors could be used on any given aircraft. [%-)]
Your best bet is to study as many detailed reference pictures as possible.
Now that I have you totally confused, we’ll see if one of the others on here can help you better than I. You’ll find that there are quite a few well informed and knowledgeable people on this forum.
Again, welcome on board.
Randie [C):-)]
Welcome, and both previous letters are correct. If you have a specific, plane in mind and reference photos that would help. Both colors were used on american military aircraft, more often the greenish hue. Just remember, to scale the color,ie make the color look correct to the size of the model. Be careful to not let the green be tooo green…and as far as a blue zinc chromate, the japanese had a slightly clear blue that was used inside many cockpits, gear bays and cowlings. Not always but often. Depending on the scarcity of paint. I will mix a clear blue with a touch of clear green and some silver and that looks pretty good to me. There is also a paint color already to go that is a bit greener, I think by model master. Gunze made something I think(not available in my area anymore).
As far as I’ve been able to determine, yellow-green zinc chromate was used in WWII aircraft wheel wells; and the darker, greener "interior green " was used inside WWII aircraft cockpits. That’s the way I’ve been painting 'em for years, anyway.
Ok, now that we know they were interchangeable for Allied forces what about the Axis aircarft? What interior colors were used?[?]
Try this; it helps explain the “shades”:
http://www.ipmsstockholm.org/magazine/2004/01/stuff_eng_interior_colours_us.htm
Thanks to all who replied. It’ll definitely help.
Steve Gorder
Just going to grind the coffee a little fine here and probably start an argument but I have been told by many A/C maintainance people that, and I quote,: " ZINC Chromate primer is not an anti corrosive product - they have a thing called paint for that. "
This will not be a problem for us until we start building models out of Aluminium and move to the sea shore.
I’ve been an aircraft mechanic for thirty years and still use zinc chromate where the aircraft mfg tells me to. The use of zinc chromate became widespread in the late 30’s and early 40’s because of the US military especially the Navy. They were used primarly as an anti-corrosive and secondarly as a primer.
As noted, the chromate came in two basic colors, green and yellow. Early testing found that if yellow chromate was used where it could be seen by the flight crews, (ie, cockpits etc), it had a tendency to make a large percentage of those people violently airsick under a wide range of conditions, causing green to be used in those areas.
In the late 40s the Navy ran some tests and determined that while the cromates worked as an anticorrisive, they were no where as effective as a coat of epoxy paint (greys in the cockpits and whites in other areas (landing gears etc). The latter also made locating liquid leaks (hydraulic fluid etc) much easier.
Light aircraft aren’t usually chromated. There are a number of reasons for this with weight and expense being for most. If you completely chromate a Cessna 150, you can increase empty weight by as much as 20 lbs, which is a significant amount for that plane and increase the price of the aircraft by as much as $1500 dollars (or more). The only civilian light aircraft that I know were chromated during construction were those aircraft produced as seaplanes or amphibians.
As far as corrosion on aircraft that are based in a salt water environment (within 50 miles of the ocean), it’s always a problem. However, the worst corrosion I ever observed in aircraft was in a group of C-150 trainers that had been operated out of an airport on the shores of Lake Michigan between Chicago and Milwaukee. We ended up and had to condemn about a third of them.
Does Testors Yellow Zinc Chromate have a slight green tint? In pictures yellow zinc chromate seems to be a slightly greenish yellow.
Yes, the Yellow tone has just the slightest hint of green to it. It is a great match to the real deal.
Thanks for posting- that was an excellent set of references. Stockholm comes through again.
They have also changed the alloys of aluminum used in aerospace since the 1940s. The Duraluminum were alloyed with up to 5% copper. It was strong but would corrode real easy. The ones used today have less copper and a lot more zinc and chromium. They are stronger and more corrosion resistant. So the zinc chromate seems to be alloyed in to the aluminum.
Nowdays rather than a primer like ZC on aluminum, the popular treatment is a chemical etch/anodize coating- any of a number of proprietary coatings. This gives an excellent adhesion and corrosion protection, and the type of primer is much less important.
When I worked at MDD in the late 70s and early 80s, the unpainted parts received from suppliers was a different color from virtually every supplier, though MDD had its own standards for color and still used ZC. What was surprising was the carbon fiber structures also got chromate primer, and once primed the carbon fiber assemblies looked identical to aluminum ones!
A final comment: Here is the standard for application http://en.m.wikipedia.org/wiki/MIL-DTL-5541
I want to thank everyone for your input. I find it fascinating how many variants of the base ZC can be found. so basically both are right it just depends when and where and what time period you are shooting for. Thanks again.
Did I read somewhere that these paints also helped prevent the build up of static electricity? I could be wrong…
I read a online manual on Zinc Chromate and it doesn’t mention anything about static electricity. For its use in the aircraft industry the zinc chromate paint is a primer for aluminium alloy. The zinc chromate inhibits the oxidation of aluminium and prevents the growth of living material on the surface protected (aka kills mold). The natural color is a greenish yellow, and varies depending on the binding agents in the primer, and the medium. Various pigments or paints were mixed with the yellow zinc chromate at the factory to make green, blue, or red. Usually the first coat was yellow, followed by a second coat of green zinc chromate. Some premixed green zinc chromate was available but not universally used. Other colors of paint would be substituted for black in mixing green zinc chromate based on the availability of paint.