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Weathering down to the aluminium?


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A while ago I saw an article about weathering , the point of which was that it generally didn't go down to bare metal. Rather it would stop at the  Zinc Chromate. There were photos of modern light a/c to back up his contention. So I'm wondering if anyone knows? I don't really trust colorized photos - some actual colour shots would be great. I ask because I see some incredible shots in black and white of seriously weathered WWII aircraft and wonder if the light bits are chromate or bare alu. Something to think about anyway

Cheers

F

 

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I guess the answer is "it depends what you're building".  Not sure that every manufacturer routinely used something like zinc chromate in any case.  But even on z-c finishes, it would still be possible to wear through it...

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Well, many WW2 aircraft weren't primed with zinc chromate anyway, so you'll have to start with a study of just which primer was used on your subject.  Spitfires used two different greys - I have been told that all Spitfire tailwheel legs remained without a top colour, at least in the early years.  I believe that German aircraft used 02 initially, but then went to a primerless paint system.  The Japanese used a red primer but this became unavailable, thus leading to the late war photos of massive peeling over certain areas.  Classic modelling errors include such heavy peeling on 1942 period Japanese types, or aluminium showing through Spitfire wooden propeller blades.  Another is wear on the front face of metal propeller blades, not the rear.  Beyond that it becomes a matter of how much wear, and of what kind?  Areas of heavy wear would include the wing roots, where ground crew in military boots would wear any paint away fairly quickly, or the very edges of access panels for rearming, levered away with screwdrivers to gain time and reduce effort.  Leading edges would get fairly heavy wear, but perhaps here and in other areas not so often down to the metal.  You would expect to see areas of exposed metal surrounded by a rim of the primer rather than (except perhaps on those ammo panels) an immediate step from camouflage to bare metal.

 

However, in many modern models weathering is less at attempt at realism than a competitive art, where the aim is a "creative" effect.

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One common mistake I often see on early A6Ms is that the modeler chips the Ame-iro paint right down to the aluminium.

Unlike the late-war greens, this paint was very durable, being specifically developed for use in harsh sea climates.

Later, when green was added to top surfaces to improve camouflage, it would chip exposing the Ame-iro patches, but rarely would it go down through to the metal... pilot step-way being the sole possible case

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Paint and finishes aren't really my bag, but here goes anyway...

 

I believe that many primers actually etch into the surface of the metal. I presume, therefore, that bare metal would show mostly where the surface finish was chipped (or pitted from ammunition propellant) or severely sand-blasted.

In this regard, I think that wear from general UV exposure, air friction and surface rubbing would mostly result in the primer being exposed (unless the aircraft's surface had not been maintained for several years)

 

These are just presumptions, somebody out there's bound to have a better answer for you. Good luck!

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As with many similar questions, this is one of those for which there is no definite answer ! There are too many factors that affect how much a finish on an aircraft wears off and if metal surfaces get exposed or not: was the type primed ? With which primer ? How many coats of paints ? Which kind of paint ? What caused the wear ? Was it abrasion from sand ? People walking over the wings to perform maintenance ? And for how long was the aircraft in service ? And where ? And what kind of corrosion control procedure was in use at the time in that unit/air force ?

Going from one extreme to the other, you may have a Japanese Army aircraft in WW2 where the finish was applied at unit level over the original bare metal finish. Such an aircraft will show bare metal very quickly, particulary if based on some pacific island. Or you may have a modern  jet painted with very tough stuff and carefully maintened with no sign of ay wear visible. Or you may have an USN jet where any time an inspection panel is removed and refitted, new paint is sprayed in place to prevent corrosion..

So the answer would be that it depends on all these factors. If you're interested in a realistic representation, best way to do is to do what I understand you're already doing: check for pictures of similar subjects. If you want to see pictures of WW2 types with weathering going down to bare metal, have a look at late war USN types, like the Corsair, that tended to suffer somewhat from wear, particularly on the leading edges They don't have to be WW2 pictures, colour pictures from the Korean War can be found more easily and represent aircraft in the same finish.

 

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40 minutes ago, warhawk said:

One common mistake I often see on early A6Ms is that the modeler chips the Ame-iro paint right down to the aluminium.

Unlike the late-war greens, this paint was very durable, being specifically developed for use in harsh sea climates.

Later, when green was added to top surfaces to improve camouflage, it would chip exposing the Ame-iro patches, but rarely would it go down through to the metal... pilot step-way being the sole possible case

Thanks for the info, this is useful to note, I'm starting an IJN collection at present.

 

The later Shinden-kai seem to have weathered very strongly and profile images appear to show the green peeling off down to bare metal, or was this actually white underpaint?

Edited by Tim R-T-C
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34 minutes ago, Graham Boak said:

These examples are where no primer was applied because of the extreme supply shortages.

Agreed. The under-surfaces (and often wheel wells - particularly on N1K2-J/-Ja) are also NMF in these cases.

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Wow! A lot to think about. Thank you all very much for the comments. My victim is one of the new Tamiya P-38s, the assembly of which is, at the risk of tempting fate, just a out me proof. A real eye opener after a couple of testors oldies! So I  really want to make a good job of the finish. As a sort of PS, if I  want to get it into the cupboard with the rest I'll have to build it wheels up on a stick.  Which would be a bit of a shame given the level of wheel well detail.

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Hmmm, perhaps a little too much wear on the paintwork. That left nacelle looks a little over-done...

 

Color+An+American+P-38+Lightning+fighter

Edited by Blimpyboy
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Is that one of those"any landing you can walk away from..." situations?

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1 minute ago, Spec7 said:

Alloy in its raw form is grey not shinny

 

 

 

The walkway her gives a good idea of whats underneath the paint...not a lot

Good point. Easy to forget.

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The visible metal skin of most parts of most metal-covered types in ww2 was not an alloy, it was a thin layer of pure AL over the duraluminum alloy substrate which provided the mechanical properties.

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3 hours ago, Tim R-T-C said:

The later Shinden-kai seem to have weathered very strongly

The Shiden-Kai was factory-painted on the top sides and left bare metal on the undersides. The IJN green was quite durable and usually didn't show much wear during operations, even if there was no primer applied (not sure if the N1K2-J was primed or not). Of course, there are some cases of more extensive chipping in some areas but mainly due to rough handling and not to natural wear. The IJN treated their equipment with care even through to the end of the war, e.g. cleaning the surface with oiled rags. 'Extensive wear' can usually be attributed to  after-surrender pictures when the aircraft had been exposed to the elements for weeks/months or 'handled' by US clear-up teams.

 

It was a little different case in the JAAF where late-war planes were often field-camouflaged.

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3 hours ago, Blimpyboy said:

I believe that many primers actually etch into the surface of the metal. I presume, therefore, that bare metal would show mostly where the surface finish was chipped (or pitted from ammunition propellant) or severely sand-blasted.

Etch primers and the like will indeed 'etch' into the surface, but only fractionally.  It would still be possible to wear through the etch layer with enough regular use/contact..

26 minutes ago, Spec7 said:

Alloy in its raw form is grey not shinny

True, but it will take on a 'polished' appearance on a wing walkway (for instance) with regular buffing from ground crew boots, etc.  It will be less polished, as you suggest, if the exposed metal is somewhere else on the aircraft.. 

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Looking at some walk around shots of P-38 wheel wells and those I've  found seem to either  be zinc chromate or light grey. One thing Aluminium does is surface oxidize, goes paler. I have done a couple of paintings on aluminium sheet and the oxide meant it didn't need priming. 

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41 minutes ago, seadog said:

Looking at some walk around shots of P-38 wheel wells and those I've  found seem to either  be zinc chromate or light grey.

Be careful there- especially if the walkarounds are of restored or museum P-38's! According to the written references I have read,  P-38's through the P-38F had wheel bays and struts finished with an aluminum lacquer; for the P-38G through L, the wheel bays and struts were painted neutral grey- in many period b&w photos, where the  struts and inner gear door surfaces appear dull or dark, this is due to the neutral grey paint. Late production P-38L's and M's were said to have reverted back to aluminum lacquer and/or zinc chromate yellow. The unrestored P-38 at the National Air and Space Museum has wheel bays and struts in neutral grey, which I can confirm, because I saw this airplane when she was stored at Silverhill, MD before she was cleaned up and moved to the Dulles Annex.

Mike

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Aluminium doesnt polish with walking on it in fact quite the opposite as its soft, it has a natural lanolin that gives it a slightly greasy surface, wash that out and thats when you see it qo white and chalky. a lot will be down to its copper and zinc content , it only really remains shinny when you polish it and the polish leaves a thin preservative on it otherwise it will dull back very quickly especially if it gets wet

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I suppose it depends on how you define 'polishing'.  Anything that abrades the surface will effectively polish it, though not necessarily to a bright finish, although it is likely to appear brighter on an area in regular use..

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The depth of knowledge on the forum always impresses me. Thank you all, I really appreciate the guidance!

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4 hours ago, Blimpyboy said:

Hmmm, perhaps a little too much wear on the paintwork. That left nacelle looks a little over-done...

 

Color+An+American+P-38+Lightning+fighter

@Blimpyboy - Cut it some slack.  It did just crash, after all...! 😉

 

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hay1-Nakajima-Ki-84-Hayate-Clark-Field-1

 

It is obvious that Japanese machines were losing paint  to bare aluminum (as above)

The US machines sometimes also

F4U-Early-GSB-768x380.jpg

I agree here some zinc chromate is also visible, not anly bare metal

The Britts sometime also

whirlwind_mk_i_263_sqn_exeter_in_flight_

sund.jpg

 

Regards

J-W

 

 

 

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14 minutes ago, Shark444 said:

Hmmm, perhaps a little too much wear on the paintwork

If that's a diorama, it's a pretty darned good one! :giggle:

Mike

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