Jérome the frenchie Posted December 11, 2008 Share Posted December 11, 2008 [This thread is the same as in the "Classic Aviation" section, sorry, it's a "prop" AND a "classical" aircraft ] Hello, a friend is restoring a real Vultee BT-13A. I am very surprised by all the inner surfaces. They are BLUE. Not Zinc Chromate (yellow) nor Interior Green (green), nor Salmon Pink like on the early Birdcage, but BLUE. Was it an usual color for the primer or is it an exception ???? I have never seen a scale model with this color. Are modelers ignore it ? Here a sample : Quote Link to post Share on other sites
Dave Fleming Posted December 11, 2008 Share Posted December 11, 2008 Interesting - is it paint or a varnish? Quote Link to post Share on other sites
Jérome the frenchie Posted December 11, 2008 Author Share Posted December 11, 2008 Interesting - is it paint or a varnish? It's a primer, not a varnish. In his plane, their is a mix of Zinc Chromate (yellow and green), and this unusual blue, depending of the parts. He's said me it was not the first time that he's saw it. A P40 had the same. Jérôme Quote Link to post Share on other sites
Jérome the frenchie Posted December 11, 2008 Author Share Posted December 11, 2008 OK, a little answer here : http://www.nationmaster.com/encyclopedia/Z...-primer-(paint) The protective effect of chromate coatings on zinc is indicated by color, progressing from clear/blue to yellow, gold, olive drab and black. Darker coatings generally provide more corrosion resistance. Chromate conversion coatings are common on everyday items such as hardware and tools and usually have a distinctive yellow color. It seems to be Zinc Chromate in its "blue" phase. Not very usual, but possible. Jérôme Quote Link to post Share on other sites
Steve N Posted December 11, 2008 Share Posted December 11, 2008 (edited) Curtiss used a translucent blue anti-corrosion "shop coat" on P-40s during assembly, but it was usually either later overpainted with Zinc Chromate or stripped off. This is the first I've seen of an opaque blue primer. I wonder if this bird originally had a blue fuselage and yellow wings, and the fuselage was simply painted blue inside and out during assembly. It's amazing how stuff like this continues to come to light after all these years. I'd suggest contacting Dana Bell. He may not have any answers, but he'd sure be interested! As an aside, I remember reading once that when Ford was building B-24s, some genius suggested that that they use different pastel shades for the interiors, and change the colors every production block. Not surprisingly, the Army Air Force rejected the idea. SN Edited December 11, 2008 by Steve N Quote Link to post Share on other sites
Jérome the frenchie Posted December 11, 2008 Author Share Posted December 11, 2008 (edited) I have red an article here : http://www.colorserver.net/history/history-zinc-chromate.htm It is said : Untinted and Tinted PrimerUS Erection & Maintenance instructions of the period often refer to "untinted" and "tinted" primer to describe raw Zinc Chromate primer and the same primer tinted with black. While black was the intended additional pigment, the instructions did not specify the formulation of colors. Therefore it is not unlikely that manufacturers felt free to pick substitute pigments when needed. A Navy memo from 1942 goes even further and recommends using Indian Red (you can see it in the back on the first picture), lamp black, or any other suitable indicator to use with a second coat of Zinc Chromate primer to distinguish between single- and double-coated surfaces. In the light of this memo, Vought's Salmon pink was also simply tinted primer. It seems to be very informal, depending of the constructor, the period, etc... Jérôme Edited December 11, 2008 by Jérome the frenchie Quote Link to post Share on other sites
john53 Posted December 11, 2008 Share Posted December 11, 2008 WOW!!! For a minute there I almost asked if it was a Mitsubishi or Nakigima built aircraft..... Quote Link to post Share on other sites
Steve N Posted December 12, 2008 Share Posted December 12, 2008 I posted those photos over on a warbird forum. One gentleman responded that he restored a pre-war BT-13A, and found the same blue paint inside and out. I think (just my personal opinion) that the fuselage was painted the standard USAAF blue inside and out prior to final assembly, but the paint was stripped off the outside later in the plane's career. You'll notice that the same blue is on the outside under the tail and horizontal stab fillets, lending credence to the idea that it was stripped down without being disassembled. SN Quote Link to post Share on other sites
C-130CrewChief Posted December 12, 2008 Share Posted December 12, 2008 What ever the original paint was on that plane the zink chromate information was realy interesting. I never knew a chemical conversion coating could be so interesting and I see it every day. Curt Quote Link to post Share on other sites
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