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plasticmasher

Spitfire walkway - primer or duralumin?

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Evening All!

Looking at pictures of my current 1/48 Tamiya Vb project, I've a question about worn walkways on Spits. Having read the whole 'Stupid Spitfire Questions' thread.....which filled in lots of stuff I didn't know I didn't know...... and having read Edgar's comments somewhere about Spitfire primer being an as yet unknown grey, prior to top coating.......is this wear likely to be exposed primer, or worn all the way to bare metal?

/EN921walkway_zpshtj2cgqs.png]

I've also found this wartime colour image, and again the wear could be through to just the grey primer (and in my experience of airframe primer, although of the zinc chromate yellow type from Boeing, and the grey-green Westland stuff; it is quite hard wearing compared to top coats).

If the image below of the 303 Sqn machine is through to the wing skin metal surface, I suppose the oxidation and weathering would lead to a dull pale grey anyhow, rather than a shiny aluminium appearance often portrayed. The only bits worn to metal I get to see on airframes are rivet heads and panel edges that see heavy foot traffic.

Any insight or suggestions that can shed a bit of light here would be welcomed.

Cheers

Ed

p.s. Recall someone metioning walkway 'patches' in the daft question thread - I think this is on the 303 Sqn machine?
polish-spitfire-zumbach%20walkway_zpspew]

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I don't know enough about metals, but the Spitfire was not made of simple aluminium; it used Alclad, which, I believe, was a form of anodised aluminium (Nick Millman, where art thou?) This possibly means that any worn areas were either grey metal or grey paint.

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Alclad is an aluminium alloy with a thin "coat" of pure aluminum on the outside- a sandwich. Pure aluminum is not near as strong, but it is far less vulnerable to corrosion.

bob

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Alclad is nearly pure Al sandwiching high strength aluminium copper alloy sheet.(Duralumin)

Duralamin is an Aluminium alloyed with Copper and a some other metals (I can't remember) sandwiched by aluminium in sheet form* to improve corrosion protection.Its stronger but corrosion resistance wasn't good without the Al sandwich.

*It gets a bit confusing because Dural clad in Al became Alclad which was another companies trade name for it.

We had sheets of Alclad but Dural sheet wasn't something I saw or heard of (I can't remember any) after training. Dural rivets ring a bell somewhere,they weren't Al coated IRC.The Duralumin name was also a company name.

So to simplify Alclad is Al coated Duralumin. My brain hurts.And SWMBO KEEPS TALKING ABOUT THE VOICE on tv! I have no idea what she is saying either.

Near pure Aluminium is L59 and wasn't used, far too soft.

Edited by bzn20

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It gets a bit confusing because Dural clad in Al became Alclad which was another companies trade name for it.

I think "ALCLAD" name came from aluminium cladding.

In France, the equivalent, "VEDAL" meant "tu d'aluminium"(A5)

the thickness of pure aluminium coat is around 1/20 of total thickness.

During build of airplanes, to prevent scratches on these surfaces, Alcald receives a coat of varnish before assembly.

Edited by BS_w

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I think "ALCLAD" name came from aluminium cladding.

In France, the equivalent, "VEDAL" meant "tu d'aluminium"(A5)

the thickness of pure aluminium coat is around 1/20 of total thickness.

During build of airplanes, to prevent scratches on these surfaces, Alcald receives a coat of varnish before assembly.

yes it does named so by ALCOA

No they don't varnish sheet metal. It comes covered (both sides) in polythene OR oiled grease proof paper shiney side against the sheet. so it doesn't scratch in transit/stores/hangar floor until used. Even band sawed or gillotined with it on. its cut filed to size,drilled off and when its correct to drawing. either sent to paint or we/I/they use fine wet and dry the surface removing fine scratches and some cladding to a satin like finish. treat with Alachrom 1200 for a few minutes. all the cut/filed/drilled edges turn brown by the Alachrom 1200 rinse with water,primed,painted with what ever the drawing calls for. If it goes to paint they follow exactly the same process but the paint job is probably better!

Edited by bzn20

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alcald Covered with polyethylene film is modern.

For example

the Curtiss aircrafts during the ww II, alcald received a coat of varnish before assembly. On the P-36 and P-40, this varnish was lionoil , tinted Prussian blue.
Finish for unpainted aluminium surface, it was necessary to remove this shop coating with solvent and brush wash .
The metal was cleaned a second time with the solvent using clean rags to remove all trace of shop coating.
Then a wahh with Neutraloïd solution, soaping swabbed, rinsing, before polishing

Edited by BS_w

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Sorry I thought we were talking about something that had been around for 60 years at least.

Edited by bzn20

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Primer or Aluminium? In your initial post you were talking in the present tense which caused my confusion. BTW that Prussian blue coating..........I've seen sheet mild steel and bar with that or something similar. The other things you mentioned have obviously superceded and by the process you described a good job it was. I'd still be on my first aircraft. Far too much washing and wiping.

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I've had a close look at some of the original Mk V Spitfire sections in our collection and I can't say that I can see any primer on any of them where paint has been worn off; it's just bare dull alloy.

Alloy needs an etch primer which is applied as a very thin coat but this would wear off with the colour coat and wouldn't appear as an area of different colour.

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