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Spitfires and Zinc Chromate (Yellow)


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#1 Daniel Cox

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Posted 18 November 2010 - 02:01 PM

Hi All,

How common was the application of Zinc Chromate (Yellow) on Spitfire Mk. IX aircraft in RAF service during the Second World War?

Specifically for application on the following parts:

1. Top, side & lower cowls.
2. Wing fillets.
3. Oleo struts, gear doors & wheel hub covers.
4. Engine mount assembly.
5. Oil Tank & associated plumbing.

Cheers,


Daniel.

P.S. Reason for edit; What evidence is there that the crowbar attached to the cockpit door on Spitfires was painted "Interior Grey Green"? I suggest they were left unpainted.

Also it may be of interest that the oil tank beneath the powerplant on at least some early Mk.IX aircraft appears to have been unpainted. Whereas later Mk.IX's appear with Interior Grey Green Oil tanks or sometimes with Zinc Chromate Yellow also applied.

Edited by Daniel Cox, 18 November 2010 - 03:22 PM.


#2 greatgonzo

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Posted 18 November 2010 - 05:33 PM

No ZCY on Spitfire. The aircrafts were primed, sure but the primer was grey, and covered with other colors on most if not all parts.

Where have these ZCY oil tanks came from? Ouite interesting.

Edited by greatgonzo, 18 November 2010 - 05:37 PM.


#3 Daniel Cox

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Posted 18 November 2010 - 05:51 PM

No ZCY on Spitfire. The aircrafts were primed, sure but the primer was grey, and covered with other colors on most if not all parts.

Where have these ZCY oil tanks came from? Ouite interesting.


Hello Greatgonzo,

Yes ZCY on Spitfires, all the parts I have previously mentioned do have ZCY applied to them. They appear on a Dull Red coded with Sky spinner No. 241 Squadron RAF Spitfire F Mk.IXc in Italy during 1944.

If it isn't ZCY then someone was somewhat overzealous with the application of yellow paint inside and out on that particular Spitfire.

Note: The individual identity of the airframe is unknown despite having a borrowed a propeller blade and or propeller from JF756 a LF Mk.VIII Spitfire.

Cheers,


Daniel.

Edited by Daniel Cox, 18 November 2010 - 06:04 PM.


#4 TheModeller

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Posted 18 November 2010 - 06:55 PM

Hello Greatgonzo,

Yes ZCY on Spitfires, all the parts I have previously mentioned do have ZCY applied to them. They appear on a Dull Red coded with Sky spinner No. 241 Squadron RAF Spitfire F Mk.IXc in Italy during 1944.

If it isn't ZCY then someone was somewhat overzealous with the application of yellow paint inside and out on that particular Spitfire.

Note: The individual identity of the airframe is unknown despite having a borrowed a propeller blade and or propeller from JF756 a LF Mk.VIII Spitfire.

Cheers,


Daniel.


Without the pic its hard to make a judgement... Do you mean this one?

Posted Image

If so then the apparent 'yellow' is far more likely to be a result of coolant overflow blowing back across various parts of the engine, bearers and oil tank.

It would be helpful if you could post the picture you're referring to.

#5 Daniel Cox

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Posted 18 November 2010 - 08:29 PM

Without the pic its hard to make a judgement... Do you mean this one?

If so then the apparent 'yellow' is far more likely to be a result of coolant overflow blowing back across various parts of the engine, bearers and oil tank.

It would be helpful if you could post the picture you're referring to.


Hello TheModeller,

Yes that is the image showing the application of Zinc Chromate (Yellow) on a Spitfire F Mk. IXc, on closer examination and with a better image the yellow appears to have been applied to specific points.

More follows below.

Posted Image
IWM TR1537

Note the application of Zinc Chromate (Yellow) on various points of the engine mount assembly and more as well as on the wing fillet. Also of interest is the Sky coloured 'slipper' tank in the image above.

Posted Image
IWM TR1537

Of interest are the cowling panels shown above with an apparently careful application of Zinc Chromate (Yellow), which argues against coolant overflow as an explanation.

Posted Image
IWM TR1537

Finally the yellow noted on the wing fillet in the first image above continues along the fillet edge, also shown are some of the numerous small applications of Zinc Chromate (Yellow) on the oleo strut amongst other parts. The yellow colour seen in the lightening holes at Frame 11 are wire conduits and are not part of the evidence of the application of the Zinc Chromate. Note also the dull red codes.

So how common was the application of Zinc Chromate (Yellow) on RAF Spitfire Mk.IX aircraft?

Cheers,


Daniel.

Edited by Daniel Cox, 07 December 2010 - 01:10 AM.


#6 TheModeller

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Posted 18 November 2010 - 08:52 PM

I wouldn't discount the coolant overflow completely, certainly the front face of the oil-tank displays exactly the kind of staining I'd expect to see from a coolant leak, the apparent similarity in colour might, I say might, be purely a coincedence.

The close up images you've got do seem to show priming or maybe re-painting with ZCY, I've never seen it before in wartime images of Spits but given the comparatively few around that are in colour that isn't really surprising.

Edgar would be the man to know for sure but from everything he's related here and on other forums his research indicates that a grey primer was most commonly used, it's possible that given the rather make-shift nature of supply-lines to Italy repairs and repaints might have made use of locally available paints and primers or even supplies loaned or liberated from American units where ZCY was far more common as a primer coat.

Edited by TheModeller, 18 November 2010 - 08:53 PM.


#7 greycap

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Posted 18 November 2010 - 09:11 PM

I wouldn't discount the coolant overflow completely, certainly the front face of the oil-tank displays exactly the kind of staining I'd expect to see from a coolant leak, the apparent similarity in colour might, I say might, be purely a coincedence.

The close up images you've got do seem to show priming or maybe re-painting with ZCY, I've never seen it before in wartime images of Spits but given the comparatively few around that are in colour that isn't really surprising.

Edgar would be the man to know for sure but from everything he's related here and on other forums his research indicates that a grey primer was most commonly used, it's possible that given the rather make-shift nature of supply-lines to Italy repairs and repaints might have made use of locally available paints and primers or even supplies loaned or liberated from American units where ZCY was far more common as a primer coat.

maybe of no direct relavence . when the wing fillet of the fighter collection spitfire 22 was removed the underneath colour was yellow. whether it was a top coat or if it was the result of a previous restoration i have no idea .but yellow it was.
regards
greycap

#8 Daniel Cox

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Posted 18 November 2010 - 10:49 PM

I wouldn't discount the coolant overflow completely, certainly the front face of the oil-tank displays exactly the kind of staining I'd expect to see from a coolant leak, the apparent similarity in colour might, I say might, be purely a coincedence.

The close up images you've got do seem to show priming or maybe re-painting with ZCY, I've never seen it before in wartime images of Spits but given the comparatively few around that are in colour that isn't really surprising.

Edgar would be the man to know for sure but from everything he's related here and on other forums his research indicates that a grey primer was most commonly used, it's possible that given the rather make-shift nature of supply-lines to Italy repairs and repaints might have made use of locally available paints and primers or even supplies loaned or liberated from American units where ZCY was far more common as a primer coat.


I have also never seen it before that is hardly a surprise though, since I'm not really a fan of the Spitfire although I do like the Mk.24 followed by the Mk.IX in order of preference all the others don't really grab me at all.

Regarding coolant as an explanation I consider this unlikely and remain unconvinced although as someone who in a former life used to work in an S2 Shop I acknowledge that your assessment may be correct. In my appreciation it looks like the application of corrosion control as opposed to the result of leaking coolant.

I am also examining images of a naked Spitfire IX in colour as captured in 1942 which incidentally has the seat flare rack on the seat albeit not installed as it is resting atop of the seat bucket. This airframe uses Interior Grey Green on many internal parts and does not have any Zinc Chromate (Yellow) apparent on any internal surfaces.

Posted Image
IWM TR1537

Can you see why I remain unconvinced?

ZYC usage may have been a theatre related event or the result of the previous USAAF usage of Spitfire airframes. That being said it is probable that the usage of ZYC may have become more widespread in the latter part of the war and beyond as further related by Greycap in the previous post. Although by whom, when, where and how often remains unanswered at this point.

Cheers,


Daniel.

Edited by Daniel Cox, 07 December 2010 - 01:10 AM.


#9 greatgonzo

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Posted 18 November 2010 - 10:59 PM

Looks like a repair pachwork to me. The possible reasons for use of the paint are mentioned above. There is also a question how real are the colors of the pic. I am not saying there's something wrong with them, just asking.
I'd be surprised to learn Spitfires were primed ZCY on production line, but it woud not be the first time really :).

#10 Daniel Cox

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Posted 18 November 2010 - 11:16 PM

There is also a question how real are the colors of the pic. I am not saying there's something wrong with them,


The pics that I have posted have sRGB IEC61966-2.1 as the embedded profile they were sourced from an Adobe RGB (1998) profiled pic, as to the original think Kodachrome.

Cheers,


Daniel.

#11 dahut

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Posted 19 November 2010 - 03:09 AM

Looks like a repair pachwork to me. The possible reasons for use of the paint are mentioned above. There is also a question how real are the colors of the pic. I am not saying there's something wrong with them, just asking.

I was thinking the same. Perhaps some chaps got hands on some USAAC ZCY and applied it here and there. Use by USAAC units at one point could also explain it, I suppose.

#12 TheModeller

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Posted 19 November 2010 - 10:40 AM

The pics that I have posted have sRGB IEC61966-2.1 as the embedded profile they were sourced from an Adobe RGB (1998) profiled pic, as to the original think Kodachrome.


Don't want to burst anyones bubble here but I seriously doubt any kind of digital reproduction of a wartime image truly reflects the actuality of the subject as photographed, there are simply too many variables possible in the process. Quality of film stock, filters used, printing process, reproduction process, scanning from print or slide, degradation of the original picture and so on...

It doesn't pay to be to pedantic about image profiles and colour tempratures and RGB values when you are dealing with 60-odd year old originals.

The paint in your pictures 'appears' to be ZCY, how it got there and how widespread the practice was is anybodys guess.

Edited by TheModeller, 19 November 2010 - 10:41 AM.


#13 Nick Millman

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Posted 19 November 2010 - 11:15 AM

FWIW the coating appears typical of the sort of maintenance applied spot corrosion prevention and component replacement/repair subsequent to manufacture still seen today. The most probable explanation is that it was the most suitable protective coating available to the maintenance teams in that location and at that time. Was this aircraft perhaps sharing airfield facilities with US maintenance units?

#14 Mike

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Posted 19 November 2010 - 11:24 AM

An uninformed comment from me - I'm no color expert, but as Martin Baker used ZCY on the MB-5 towards the very end of WWII, could it not be that it was just starting to trickle into use when that photo was taken? Perhaps as someone suggested, some was used to patch paint the airframe in the picture, and it wasn't US stores at all?

#15 Nick Millman

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Posted 19 November 2010 - 11:33 AM

An uninformed comment from me - I'm no color expert, but as Martin Baker used ZCY on the MB-5 towards the very end of WWII, could it not be that it was just starting to trickle into use when that photo was taken? Perhaps as someone suggested, some was used to patch paint the airframe in the picture, and it wasn't US stores at all?


Hi Mike, it's a fallacy that "ZCY" was not used by/available to the British. I've posted about this before but Zinc Chromate, ZnCrO4, is generally a bright yellow (but some do describe it as a greenish yellow) and crystalline in form. When used as a pigment (one of a family of pigments) in anti-corrosive primer paints it was usually referred to as Zinc Yellow or Yellow 36. There are many possible variations and combinations for its use in primer and paint form, with a variety of colourings, some of which are proprietory and include even an orange. Its use was not restricted to US military aircraft production, although in the modelling field it seems to have become synonimous as a unique US aircraft paint colour.

Zinc chromate "yellow" and zinc chromate "green" are just descriptive usages. Zinc chromate green was applied the Spitfire prototype.

It has been commercially produced since 1850 and long recognised as an effective corrosion inhibitor, in later years especially for magnesium alloys.

Edited by Nick Millman, 19 November 2010 - 11:37 AM.


#16 dahut

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Posted 19 November 2010 - 12:55 PM

Hi Mike, it's a fallacy that "ZCY" was not used by/available to the British. I've posted about this before but Zinc Chromate, ZnCrO4, is generally a bright yellow (but some do describe it as a greenish yellow) and crystalline in form. When used as a pigment (one of a family of pigments) in anti-corrosive primer paints it was usually referred to as Zinc Yellow or Yellow 36. There are many possible variations and combinations for its use in primer and paint form, with a variety of colourings, some of which are proprietory and include even an orange. Its use was not restricted to US military aircraft production, although in the modelling field it seems to have become synonimous as a unique US aircraft paint colour.

Zinc chromate "yellow" and zinc chromate "green" are just descriptive usages. Zinc chromate green was applied the Spitfire prototype.

It has been commercially produced since 1850 and long recognised as an effective corrosion inhibitor, in later years especially for magnesium alloys.

Wow nick that is astonishing that you would know that. Fascinating stuff, really. Ive used a lot of ZC, US MilSpec variety, being in the US NAVY for a decade. I commandeered many spray cans of it back then and only recently used the last of it up. I can tell you the mil-issue spray in a can is a crappy model finish!

#17 Daniel Cox

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Posted 19 November 2010 - 08:34 PM

Hi All,

Zinc Chromate (Yellow) is also found on some of the internal surfaces within the fuselage after Frame 11 of Spitfire LF Mk.IXe TE565.

Cheers,


Daniel Cox.

#18 Daniel Cox

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Posted 19 November 2010 - 09:32 PM

Don't want to burst anyones bubble here but I seriously doubt any kind of digital reproduction of a wartime image truly reflects the actuality of the subject as photographed, there are simply too many variables possible in the process. Quality of film stock, filters used, printing process, reproduction process, scanning from print or slide, degradation of the original picture and so on...

It doesn't pay to be to pedantic about image profiles and colour tempratures and RGB values when you are dealing with 60-odd year old originals.

The paint in your pictures 'appears' to be ZCY, how it got there and how widespread the practice was is anybodys guess.


Hello TheModeller,

I am well aware of issues regarding colour reproduction from my own professional experience in this area including amongst other work experience in Printing, Photography, Graphic Design and illustration. I also have experience maintaining image library collections for the media (love that vinegar smell as immense quantities of old negatives go south).

It can't hurt to be pedantic either, some colour and some effort is better than none at all and I did pay for the opportunity.

Could that be Zinc Chromate (Yellow) on the hangar structure shown below behind the Spitfire F Mk.IXc spinner, seat and wing in England during November of 1942?

Posted Image
IWM TR514

As an addition here is a pic below showing the crowbar as affixed to the cockpit door on a Spitfire F Mk.IXc Note the colour of the crow bar which is clearly not Grey-Green in fact it is worth noting I have been unable to find any colour pictures from the era that show the crowbar was ever painted Grey-Green or of course Red either.

Posted Image
IWM TR514

It is worth looking in; Ethel, Jeffrey L., Sand, Robert T. Fighter Command, Motorbooks International, Osceola, 1991. p. 32, 36, 122. for further examples of this.

Cheers,


Daniel.

Edited by Daniel Cox, 07 December 2010 - 01:11 AM.


#19 TheModeller

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Posted 19 November 2010 - 10:23 PM

Are those girders/trusses painted ZCY? Isn't just as likely they may be white, cream or insignia yellow and the tone is being affected because they are in deep shadow?

In a closed hangar, particularly on a wartime airfield, I'd have thought painting such sections a light colour would have been sensible to avoid collisions and potential damage while moving aircraft around. Whether the notion holds up or not is anyones guess of course, it just seems logical. To be honest, ground handling, maintenance procedures, working practices and systems used by RAF ground crew during the war are a subject I have yet to see any detailed discussion or documentation about. I always thought it might make for an interesting book, if only for a somewhat limited audience!

As an addition here is a pic below showing the crowbar as affixed to the cockpit door on a Spitfire F Mk.IXc Note the colour of the crow bar which is clearly not Grey-Green in fact it is worth noting I have been unable to find any colour pictures from the era that show the crowbar was ever painted Grey-Green or of course Red either.

Posted Image


Yes I think its pretty widely known now that these crowbars were either painted IGG or left in bare metal, of course if you have access to more period colour images then you'd be better placed to make a judgement about how often they were painted as opposed to bare metal. But just because you haven't found any colour pictures of crowbars painted IGG doesn't mean they never were. We agree that colour period images are pretty thin on the ground.

Again the documentation Edgar Brooks has discovered in the NRO at Kew detail standard factory applied finishes, in the absence of colour pictures I'll take a written document as sufficient.

Edited by TheModeller, 19 November 2010 - 10:30 PM.


#20 Daniel Cox

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Posted 19 November 2010 - 11:20 PM

Are those girders/trusses painted ZCY? Isn't just as likely they may be white, cream or insignia yellow and the tone is being affected because they are in deep shadow?

In a closed hangar, particularly on a wartime airfield, I'd have thought painting such sections a light colour would have been sensible to avoid collisions and potential damage while moving aircraft around. Whether the notion holds up or not is anyones guess of course, it just seems logical. To be honest, ground handling, maintenance procedures, working practices and systems used by RAF ground crew during the war are a subject I have yet to see any detailed discussion or documentation about. I always thought it might make for an interesting book, if only for a somewhat limited audience!


What was shown was illuminated by natural light from the front and via windows, do you really believe the interior is White despite the evidence shown? Even the parts in shadow do not appear to be white or cream or pink or ...

Posted Image
IWM TR514

The hangar shown above is an "Over" Blister type constructed of steel arched ribs clad with corrugated iron, the span is 65'. The hangar shown has the typical canvas curtain suspended on the rear side.

Cheers,


Daniel.

Edited by Daniel Cox, 07 December 2010 - 01:11 AM.