[WWI] SPAD 13 Internal fitting

Mark Shannon shingend at ix.netcom.com
Fri Apr 20 18:20:18 EDT 2007

Parts were, parts weren't.  Most of the British aircraft were flown cross
channel, at some point.  It just depends on what the government
specifications were for protective coatings on various parts.  I was also
responding to the comments about the second world unpleasantness aircraft
-- the idea of the aircraft seeing service anywhere around the Empire and
Commonwealth, and the emphasis on coastal defense for the USAAC as well as
the Navy needs kind of ruled it necessary.  

By the way, the Hall process for making aluminum was over 25 years old by
the time WWI rolled around (Invented 1886 in U.S. and France, first plant
opened in U.S. in 1888) -- made aluminum a commodity metal.  The
Haber-Bosch process for making ammonia and nitrates was only about eight
years old, and the Germans were relying on it to make nitrates.  Something
to do with the Chilean guano supplies being on the other side of the Royal
Navy, I think.

Anyway, aluminum may or may not have been coated post passivation,
depending on service.  The oxide coating was not that brittle, but belt and
suspenders sometimes is the guide.  Mass production for war can lead to
shortcuts and re-consideration of the necessity, but the 'preference' is
for maximum protection of structural integrity and durability.    

Mark Shannon
shingend at ix.netcom.com

> [Original Message]
> From: Joel Christy <jbarchristy at yahoo.co.uk>
> To: World War I Modeling Mailing List <wwi at wwi-models.org>
> Date: 4/20/2007 5:03:46 AM
> Subject: Re: [WWI] SPAD 13 Internal fitting
> The Westerm Front was helleva long paddle from the sea ! And brsides,
most WWI aircraft wouldn't have lasted long enough to corrode, IMHO.
>   Joel
> Mark Shannon <shingend at ix.netcom.com> wrote:
>   Salt water corrosion was a big factor in all of this. Salt can disrupt
> oxide coating and start creating pits that spall the oxide off so the pit
> grows. A very effective demonstration is to dip aluminum foil in a
> mercuric chloride solution (rinsing off the excess solution). The sheet
> will oxidize fast enough that it will become too hot to handle and flecks
> of aluminum oxide will puff up into the air. That is a case where the
> mercury and chloride work together, and is extreme, but other salts will
> cause the same mechanism at a slower pace.
> A metallurgy reference such as the Chemical Rubber Company Handbook (CRC)
> will list the compositions of many of the older alloys -- including the
> specific maritime bronze and brass alloys. (The original company is
> defunct, but the reference book lives on) Well primered and painted
> aluminum is handy in aircraft, since you never know if it is going to end
> up at an ocean side airstrip.
> Mark Shannon
> shingend at ix.netcom.com
> > [Original Message]
> > From: Ivan Carlos Ruchesi 
> > To: World War I Modeling Mailing List 
> > Date: 4/18/2007 8:05:27 AM
> > Subject: Re: [WWI] SPAD 13 Internal fitting
> >
> >
> >
> > 
> > >Yes, you are quite correct, the reference was to aluminium and not
> >internal fittings in general. However, if it was the case that there was
> >no benefit to coating aluminium then surely they changed their minds
> >about this before the second great unpleasantness? Offhand, I can't
> of any bare metal cockpits from WWII, or even the early >thirties.
> aircraft for instance corroded very badly and >relatively quickly even
> though they were constructed of >duraluminium. Even in the harsh
> environment of the Pacific theatre >the material allied aircraft were
> constructed from fared far better.
> >
> > >And I still maintain that the added weight of coating a few bits of
> >metal in OT aircraft would be so small as to be completely
> >
> > >Andy
> > 
> > 
> > Like aluminium, several metals produce a thin oxide layer on their
> surfaces to protect themselves from a more profound corrosion, e.g.
> brass, bronze, zinc, etc, this phenomen being called "pasivacion" in
> Spanish. This is what allow brass ship propellers to last a long time
> working in salt water. The problem arises, like in canned food, when the
> surface layer is punctuated, then the bare metal is quickly corroded by
> oxigen. Perhaps the paint coatings are intended to protect that oxide
> layer...
> > 
> > Ivan
> ---------------------------------
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