Warbird Information Exchange

Just wondering...were the innards of Corsairs salmon-colored? I was unaware, if so. Comments?

http://www.hyperscale.com/2017/features ... 32sp_1.htm

Yes, they were, but it was referred to as "Salmon", since it was more pink than red. This was confirmed on the F4U-1 Birdcage Corsair that was recovered from Lake Michigan a few years back. Do a search here for those threads, as there were extensive conversations about it then, as well as pictures confirming the Salmon coloring.

The salmon color was achieved by Vought by mixing "Indian Red" pigment with zinc chromate primer. This was done so as to clearly provide indication of complete coverage of a second primer coat on parts, covering an initial first primer coat of raw (yellow) zinc chromate. (In a similar reference, North American Aviation mixed black pigment with zinc chromate to make a green color for use in second-coat coverage over raw (yellow) zinc chromate for parts that required two coats of primer on their airplanes, for the same reason.)

The use of the red pigment was ordered to come to an end in the spring of 1943, and by the summer of '43 Vought began switching its practice to using only raw (yellow) zinc chromate even on two-coated parts. At this point, they used a system of ink-stamping parts after the first coat had been applied, and then by applying a second coat of raw (yellow) zinc chromate, workers could see that the ink-stamped words, which would still bleed through, were partially obscured and confirming two coats had been applied.

As stated, when the F4U-1 BuNo.02465 was recovered from Lake Michigan in 2010, it confirmed the use of the red pigmented zinc chromate throughout the airframe, with areas of yellow zinc chromate showing in some areas where the upper coat of salmon primer had been worn/eaten away. Outwardly, without opening up panels, or poking your head up inside the tailwheel well, one would never see this salmon-colored primer, as the main wheel wells, wing fold section and interior of the cowling were painted the same color as the lower surfaces of the aircraft, and the cockpit was painted green (dark dull green on early models, and interior green on later models (by/around which time the salmon primer was already done away with)). The gun bays, engine accessory section, etc., were all salmon-color due to the red-pigmented zinc chromate. As depicted in the model, on the recovered F4U-1 02465, evidence shows that the outer-facing sides of the skins were only covered in one coat of raw (yellow) zinc chromate, so yellow would be the color showing through probably most any worn/chipped paint on the exterior.

I never knew that, very interesting! So, I assume that this is the reason why on P-51's, some parts were "yellow" and some were "zinc chromate"? Even though both were primer, it just designated parts which had either one or two coasts of primer? Is that correct? Was this a standard at other plants as well? Was this done on P-38's, P-40's, P-47's, etc.?

Yes, that is correct. "Yellow zinc chromate" is just zinc chromate in its raw form, and "green zinc chromate" is the result of mixing zinc chromate with black pigment. NAA used its own mixes of "green zinc chromate" as the second coat on parts requiring two coats of primer, but as restoration companies have found, NAA would also sometimes use "green zinc chromate" on single-coated parts as well, if for instance a batch of raw (yellow) zinc chromate wasn't immediately available, in order to keep up the pace of production. Stamped aluminum parts and aluminum forgings were only required to be treated with one coat of raw zinc chromate, while magnezium-based parts were required to be treated with two coats, with the second coat being indicated by being green. Stamped parts that had to be spot welded together had to be left bare, and would only have been able to be treated with primer if time allowed after the assembly was completed. Alclad skins and brackets usually never had to be treated with primer and were left as is. Stainless steel parts/skins in contact with aluminum parts/skins had to have a coating of raw zinc chromate between them to prevent dissimilar metal corrosion. All of this leads to the patchworks of bare aluminum, yellows and greens throughout authentic B-25, T-6 and Mustang airframes.

With regard to Lockheed P-38's, the standard finishing process was just to use raw (yellow) zinc chromate throughout, while the wheel wells and possibly engine bay areas were coated in aluminum paint, which was very durable/protected well (NAA also is known to have used aluminum paint early on in the war in a similar manner, such as applied to the engine mounts on early/Allison-engined Mustangs and perhaps to the landing gear wells on those early Mustangs). On Republic P-47 production, the standard finishing process again was also primarily just to use raw (yellow) zinc chromate throughout, but the engine mounts and oil tanks seem to have always been finished in green zinc chromate. Again, with Curtiss P-40 production, I believe predominantly was just the use of raw (yellow) zinc chromate throughout. Preserved P-39's and P-63's that I have seen have a mixed use of mainly raw (yellow) zinc chromate throughout and green zinc chromate on cast parts. Grumman actually used a grey-colored primer of their own creation.

Of course "interior green" paint, as applied to cockpits, was another matter, but was also based on raw (yellow) zinc chromate being mixed with black pigment to create a green color, which, typically beginning in/around mid 1943, replaced the dark dull green and bronze green cockpit finishes on earlier-produced aircraft, and aluminum-painted cockpits before that. Cockpits could not be left in raw (yellow) zinc chromate, as it was felt to cause too much eye strain/fatigue over long periods.

Thanks for the info, John, I learned a lot!

Yes, thank you John; great explanations...I learned a lot from your answers, and from you too, OD/NG...many thanks!

-Tom

Looks like Pink to me.

_________________
45-47=-2

And what did You expect?

John has not left much space to add anything here. Very good point there.
Still, there are few things.
The colour of the protection paint was not of importance. Contrary to camouflage colours. The problem of tonal continuity of these is another story. With protection paint it didn't mutter much. Hence the different ideas of recognising the second coat.

Silver, aluminium paint was a good choice, but aluminium became strategic, unavailable material. The aluminium powder added to ZCY produced zinc chromate green, so called apple green. Aluminium was changed for black paint and new colour appeared. It was used in cockpits as a finish layer (P-51 e.g.). After JAC meetings the colour got standardised as ANA 611 Interior Green. So apple green gone and forgotten. Well, Vought has found somewhere stocks of apple green paint and got permission to use it in Corsair production. So way into F4U-1D line, Corsairs presented apple green cockpits for awhile.
The other thing is some parts could have been painted in different ways, but still according to standards. Older stocks, subcontractors, all this stuff. This means the cockpits and other inner spaces could have looked a bit patchwork like.

Another thing is camouflage changes. When F4U production started, using Light Grey for wheel wells, wheel struts and cowlings was a logical choice. When so called three colour scheme with white underside entered, the stocks of LG paint were still available. So unlogical now practice continued and LG wells and cowlings saw F4U-1Ds coming out of the line.

Producers had their own ideas about finishing their aircraft and usually got permission to proceed. Lockheed stopped painting the undercarriage and wells with Neutral Grey somewhere around H-5 model IIRC. Grumman used their Grumman Gray with success.

To add some confusion there came a problem of fulfilling large orders and ideas of speeding up the production with reduction of protective coats. Navy was solid here, planes needed their protection coming out to sea with its unfriendly environment. It was easier with Mitchell Field. Some producers (NAA, Boeing...) asked and were given. The typical lifetime of operational army plane was so short the idea looked to make sense. The protection was reduced. In theory there were two ways of doing. Protect the construction and leave skinning untouched, or the other way round. It was done and the result is seen on many aircraft, but unfortunately corrosion mechanisms were not informed. Different alloys touching each other corroded and calls about the problems soon reached the factories. Provisions had to be made. It is hard to go into details here, but for example, the recognising of precise looks of the wheel wells of any given P-51 is a nightmare for modellers and enthusiasts.
We know that with early Merlin Mustangs wells were unpainted except the main spar covered with ZCY and possibly some other elements painted likewise. Now, name the other elements! Late P-51Ds offered asymmetrical painted wells with ZCY, IG and natural metal finish present. Wonderfully reconstructed 'Happy Jack's Go Buggy' show us the scheme today. In the end the wells came back to full protection with ZCY all over them.

Another idea was chemical protection. For example the inner side of P-47 cowlings was anodised NMF throughout production.

And there are other materials like fabric, which was primed with dedicated dopes not connected with ZC family at all.

So, it is all clear here, only a man is walking on an mine field.

_________________