[ARC5] Mil Circular Material Questions

[Richard Knoppow]

----- Original Message ----- 
From: "J. Forster" <jfor at quikus.com>
To: <ARC5 at mailman.QTH.net>; <Milsurplus at mailman.QTH.net>
Cc: <Vintage-Military-RADAR at yahoogroups.com>; 
<VMARS at yahoogroups.com>
Sent: Thursday, March 27, 2014 10:12 AM
Subject: [ARC5] Mil Circular Material Questions


>I have noticed that the Cannon style (Circular, course 
>pitch Acme [square
> thread form] screw) used in several WW II systens, like 
> the ARB, MN-26,
> RA-10, and others tend to corrode more than other 
> connector types.
>
> This especially applies to the matte finish WWII 
> production, and is less
> of an issue in the bright finish post-war production.
>
> Does anyone know about the Aluminum alloy used to cast the 
> connector
> bodies? Is it perhaps high in Magnesium which is more 
> reactive and tends
> to rot in moist environments?
>
> Also, does anyone know of a way of removing light 
> corrosion, preferably
> chemically?
>
> Thanks,
>
> -John
>
    I am not sure these connectors were made of aluminum. 
Especially during WW-2 aluminum was in very short supply. It 
may be cast zinc or "pot metal" which is a rather indefinite 
alloy of zinc and other metals. .  This can suffer from 
something called zinc pest. The symptoms are a whitish 
granular deposit on the surface. Zinc pets also causes zinc 
items to become warped and distorted and to crack and break. 
Some other metals produce white deposits on the surface. 
Zinc will sometimes have a coating of zinc oxide in the form 
of a fine, whitish, powder. This actually protects the metal 
and should not be removed. I don't think cadmium causes such 
a deposit but am not sure. The shells would not have been 
made of cadmium but might have been plated with it.


--
Richard Knoppow
Los Angeles
WB6KBL
dickburk at ix.netcom.com