[ARC5] [Vintage-Military-RADAR] Re: [Milsurplus] Mil Circular Material Questions

[J. Forster]

> I don't know the specific alloys involved with the castings or knurled
> nuts, but I believe they are both aluminum alloys, John.

That's what I think also, although I think the alloy has more Mg in it
than current alloys, hence the corrosion issues.


> The castings
> respond well with glass bead blasting...perhaps a gem tumbler would
> provide the same effect but I would suggest doing only one at a time.

Well, I'd really rather not have to remove the connectors from the
chassis. That's the nexus of thye matter. I'd like to find a way of
cleaning off the corrosion in situ.

> The bead blasting is the original finish, and it does present a more
> reactive surface to moist air, but aluminum has a self-anodizing
> characteristic over time.

Yes, it self-passivates. Anodizing also creates an Al2O3 film, but thicker
and faster.

> The nut rings appear to be extrusions that are then fully machined, based
> on their bright original condition.  I use a very fine wire brush on them,
> followed by immersion in aluminum etching solution available from a
> professional paint supplier.

The etchant is either NaOH or KOH most like;ly...  both strong alkalis.

Thanks,

-John

=================


> Its efficacy depends on the extent of
> corrosion, but they generally turn out fairly well.
>
> 73,
> -Mike. KC4TOS
>
>> On Mar 27, 2014, at 1:12 PM, "J. Forster" <jfor at quikus.com> wrote:
>>
>> 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
>>
>> ===============
>>
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