A Question and A Can of Worms

Modeling Subjects Aircraft
1

Hey guys hope you can help me out with this one, I have been thinking about it for quite sometime now having joined the Before They Were Aces GB. In doing research for my build, looking at a bunch of pictures and bio’s, this question kept popping into my head. Were the so called natural metal finishes really bare aluminum or were they actually painted gray or silver. I would think they would have had a huge problem with corrosion with bare metal in both the Pacific and European theaters. Saltwater will literally eat aluminum is a surprisingly short time, and just having moisture between panels would be a maintenance nightmare.

Hope someone can set my mind at ease on this one. Kinda ironic really as I host the NMF GB LOL

2

Just a guess that PTO NMF airplanes were gloss or semi-gloss clear coated to seal out moisture and corrosion that went with it. From the color photographs and late war camera segments I would say none were silver paint as the shine is too NMF for that.[2cnts]

Another possibility is the bare aluminum was polished to keep corrosion at bay. Kerosene rubbed on aluminum can achieve a shine like a mirror, case in point is the ‘show’ P-51s that are highly polished. Modern aluminum polish is a diluted version Kerosene with other additives.[*]

3

Some where painted silver

4

I was always under the impression the reason for the NMF was to save weight at a time when the US was dominant in the skys of Europe and the Pacific. But i know what you mean when looking at pictures, some do seem to look as though they have been painted. I can’t say for certain, but all the referances say natural metal. I am sure if they had of been painted silver we would know about it. NMF did carry on after WW 2 into the 50’s, and for Soviet aircraft at least some time after.

5

[dto:]…this is a fact. In fact, many American a/c had their join lines and rivet sinks puttied over for a better aerodynamic effect at the factory (such as the Mustang) and only silver paint would hide those putty seams. Early in the ETO airwar most American a/c wore camo; as the fortunes of war turned against the Germans, many felt the camo was unnecessary…

6

having lived in the south Pacific for awhile, I can tell you upfront that the intense sunlight did more damage than the salty air. Add that with the heat (in some areas), and everything that’s non metalic just rots. But it will also take an even harsher turn for the worst during the monsoon season, as water and aluminium just don’t like each other.

gary

7

While natural aluminum will corrode rapidly, that is not true of Alclad aluminum, which is what the alclad process was for. What Alclad is, is a pure aluminum layer rolled on to the outer surfaces of aluminum alloy. This pure aluminum layer will corrode and form a barrier to corrosion on the underlying alloy. That was sufficient for the intended lifetime of the wartime aircraft, which was 3 or 4 years if that. Although the wings of P-51’s were lacquer coated to get the best laminar flow conditions, this was not done on P-47’s or P-38’s, for instance. The Navy aircraft were painted as open ocean operations were a much harsher environment than land based operations.

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John has it right. Check out this small article on Alclad. It mentions the the effects of salt corrosion.

http://en.wikipedia.org/wiki/Alclad[](http://farm3.static.flickr.com/2478/4193091967_8bd11b5840_o.gif)

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Jeaton01 I was a machinist for 30 years in aerospace and I did think of alclad. However when alclad corrodes it turns a white color and pits pretty badly. I dont see that in any of the pictures I have looked at. Alclad with a clear coat on it may have been what they did. I wouldn’t think it was used on the show birds though because its only a few thousands thick and would polish off very quickly leaving a very uneven shine. I could be very wrong about that though.

10

NAA did not, as far as I have ever seen, do this with the entire aircraft, ever. However, on P-51D’s, they did putty, sand, and paint silver much of the wing. The entire wing, top and bottom, was puttied and painted silver except for three parts:

landing gear doors

control surfaces

central access hatch for fuel tanks, on the bottom of the wing

The entire rest of the wings, including gun bay access hatches, was painted silver. This was because of the laminar flow wing–they did it because they thought it would increase the wing’s performance. To the best of my memory, NAA did not ever at any time do this to the entire aircraft. Early on they used to paint the planes in the OD green, but once the AAF stopped using the camo paint on fighters, then the planes were bare metal except for those wings.

Something else–I recall a documentary about Mustang pilots, I believe it was Bud Anderson, but could have been another pilot. He was talking about how the order came to remove camo paint from planes in the field, and the crew chiefs and maintenance guys spent a whole night washing the paint off of his plane using avgas. He said his crew chief’s hands were all bloodied up from the job. Aha, I just found it, this can be found in his book, “To fly and fight”. Here’s some more detail, look on the top of page 4:

http://www.eaa55.org/Wingtips/wingtips2005/SEP%2005%20Wingtips.pdf

After flying a mission late in 1944, Bud mentioned to his crew chiefs that there had been snow on the continent that day, and it was time to think about stripping the olive drab paint off the airplane to make it less visible in combat. He knew this would be a painstaking job, and that few chemicals were available to do it. But, he figured that they could do a little bit at a time, and eventually get the job done. He was shocked the next day when he went out to fly and the airplane was completely back to natural aluminum. Overnight, the maintenance men had completely stripped the airplane using aviation fuel as the solvent. Bud said their hands were cracked and bloody, but they were proud that the airplane was again ready for fly with the best possible combat edge for the pilot.

Keep this in mind now, when a Mustang wore camo paint, didnt the wings also have the same paint? So they would have stripped the wings too.

If youre looking to do a newer bird, as in low-time in service, then the wings would likely have still been painted. But a plane thats been flying in theater for a while, well, it would depend on any number of things.

11

Dana Bell covered this subject fairly well in his books on USAAF colors. There were varying opinions on the value of camo paint, weight saving, corrosion protection, and added speed. In a nutshell, usually the closer a unit was to the battle area and the more contested the air combat, the more the value of camo paint was enhanced to the users. Testing proved that the speed difference was minimal, and weight savings as well. The biggest advantages were in corrosion protection and production speed up times. All that being said, due to the short life span of combat aircraft (late model aircraft that were in NMF only flew combat missions for roughly a year in the ETO and and only four months longer in the PTO/CBI. Due to the availability of replacement aircraft and parts corrosion did not seem to be a problem. Aircraft were worn out due to high optempo or enemy action usually before corrosion became a factor.

All that being said, most aircraft in NMF were exactly that-NMF. The Mustang has already been covered- the laminar flow wings were aluminum lacquered while the remainder of the aircraft was bare metal. Other USAAF types were all bare metal.

The USN is another matter- they used aluminum lacquer and dope from early on. And post war USAF jets, primarily the Century Series, went from NMF to Aluminum Lacquer for corrosion control in the early 1960s.

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Thank you guys very much, my question has been answered. I became confused reading about NMF in my research and knew I was asking the right group here. Again thanks a bunch.

13

I’ll argue that point with anybody. Aluminum will corrode in water. All alloys of aluminum will do that to a certain extent. It’s even worse in mineral free deionized water.

gary

14

according to detail and scale’s p-51 volumes,mustangs had silver painted wings when they left the factory; the fuselages were usually camo’d. check pictures of period aircraft,not warbirds…! hope this helps-s

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I do not see anything that supports that, though. Every photo I have found of any model Mustang in camo shows the wings are also camo. I’m talking about factory photos, shots while the planes are still in the US, and operational pics too.

16

This doesn’t really help with the paint debate, but these are two nice examples of the way aluminum can look under different care. Both Mitchells were shot at the Doolittle Reunion in April. Rick

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Having just tested on aircraft corrosion last week, I’d like to offer some additional input on the subject. Hot, humid environments are most conducive to corrosion–therefore, you never see a naval aircraft without paint (which is the best corrosion barrier). Aircraft based in England would be more likely to have natural metal finishes. Polish is also a good corrosion barrier, but I’m not sure if unpainted P-51s (as an example) would have been polished, clear-coated, or left alone.

Alclad was mentioned previously; it’s used because pure aluminum doesn’t possess ideal strength and copper alloys are susceptible to intergranular corrosion (which occurs internally, along grain boundaries of an alloy, and results from improper heat-treating).

There is a lot more to aircraft corrosion, but I won’t elaborate, as some forms are difficult or impossible to replicate on a model, and much of it is outside the scope of this thread.

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as we all know NMF is not the easiest thing to apply to models. that said if those guys back then only new how hard it would be in the future for us modelers they would have camoflaged everything [clwn]

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ROFLMAO!!! you are so right DURR [proplr]

20

Back in the day paintball consumed my free time and $. I would polish the handle grip on one gun until it had a mirror finish like the Mitchel pictured above. A few hours playing while sweating and it would look like the top photograph.