Subject: Anyone know whats in GUN BLUE?

From: [email-masked] (Curt)
Date: 26 Jan 1995 10:46:11 GMT

Does anyone know what the 25 cents worth of chemicals are inside the
little 5 dollar bottle of Cold Blue at the gun store?
.
I know it is primarily a Nitric Acid solution but I have no idea what
strength or what else is in there.
.
I'm rebuilding a vacuum pump whose internal parts have suffered some
pretty extreme oxidation, from exposure to acids.
.
After removing the scale with fine sandblast I would like to do a 'cold
blue' or rust conversion before lubricating and reassembling.  It seems
that gun blue would be ideal for this.  It does a good enough job for
parts that are going to be submerged in oil anyway. Easy to use,
neutralizes with water,  not strong enough to do any harm.
.
Trouble is, I'm gonna need about a half a gallon of the stuff.  That would
be about 300 dollars at the gun store.
.
Any comments are welcome

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From: [email-masked] (Mike Rehmus)
Date: 26 Jan 1995 19:23:15 GMT

In <[email-masked]> [email-masked] (Curt) 

>be about 300 dollars at the gun store.

You need to get a gunsmithing book that talks about the different types 
of bluing.  Many of them are off-the-shelf ingredients. Cold blue is not 
a good answer, I think.  It is much more delicate than the more 
traditional types of bluing.

I assume you are not going to 'sandblast' any machined surfaces that 
need to operate with close tolerances.  I'd use walnut shells or 
something else that does not alter the surface finish of the metal.

If the pump will be submerged in oil, you don't, in general, need any 
surface finish as the oil will protect the metal in the pump.  If the 
corrosion occured in the gas side of the pump, bluing won't help at all 
because as you note, it must be protected by oil.  Course I don't know 
much about vacuum pumps.

Best,
Mike