[AT] Classic Blast

[Grant Brians]

All, the use of appropriately sized walnut shell pieces as a blast media has
been documented for decades for use on wood pieces and soft metal. The
challenge for those of us who grow walnuts has always been getting the
pieces the right size. I have never found the correct size to go through a
blast system locally. In the 1930's there were a variety of articles in
machining publications about use of walnut shells. I do not know if there is
a difference between the use of California black walnut shells and English
Walnut shells, but there might be as the black walnut shells are harder.
    In short this information provided by Mr. Deardorff makes sense. Also
his comment about rust protection could be due in part to the consumption of
the Aluminum Oxide or something about the annealing action of the blasting
with the combination. It would probably take electron microscope
investigation to be certain....
        Grant Brians
        Hollister, California
----- Original Message ----- 
From: "james deardorff" <jdeardorffsupct at yahoo.com>
To: "Antique tractor email discussion group" <at at lists.antique-tractor.com>
Sent: Tuesday, January 11, 2005 7:55 AM
Subject: Re: [AT] Classic Blast


> Bruce,
> Received your e-mail.  Here are some answers to your questions.
> -Yes, I do change the original blend after using 10 times.  The aluminum
oxide loses I estimate
>    5% of its mass per application, there seems to be no effect on the
walnut shells mass up to
>    100 uses.  So, after 10 uses I usually add 25 lbs of aluminum oxide per
8 hour day.  From
>    my use of this process over the last 8 years it seems by adding this
amount per day you     never
>    run out of productive material.  (I run the used media through the
cleaner I built after every
>    use to remove dust and paint chips).
> -I usually set my presure at 35psi (pot pressure) for cars and 45 to 50
psi for tractors.  Nozzle
>   distance from a surface approximately 12 to 15 inches at a 30 to 45
degree angle.  For deep
>    pit rust I do a primary blast at a 45 degree angle to remove old paint
and surface rust, then
>    I do a 2nd blast at 90 degrees to the surface to get out the pit rust.
I have developed a "feel"
>    for how much pressure to use on thin gauge metals.  I lay my hand on
the metal and
>    feel the vibration.  I have done enough jobs to be able to judge
pressure setting by this vibration.
> -My customers and myself have always be amazed at the way this media blend
can prevent
>    rusting for extended periods of time (I have heard reports over a
year).  I beleive there are
>   several reasons for this.  First, I do not produce excessive roughness
like regular blasting.
>    (usually less than 1 mil, 1000 th of an inch).  This gives moisture
less area to bond with.
>    I have talked to several people at the Univ of Missouri about a walnut
residue preventing rust.
>    because of the number of times I reuse the blend that there could be
much
>   walnut tanic oil deposited on the metal surface.  A phd told me that it
only takes a layer one
>    atom thick to stop rust.  Also, there is no negative effect on paint
because there is a greater
>   attraction to the paint than the tanic oil.  I have talked to NASA's
Surface Contamination
>   Analysis Technology (SCAT Team) at Marshall Space Flight Center about
this phenomenon.
>    They are interested in  testing this process as a cheap and simple way
reduce underfilm
>    corrosion activity for protective coating systems.  I have always felt
that the use of this
>    type of cleaning could double the service life of most paint systems
especially in harsh
>    chemical environments like fertilizer facilities.
>    I have written a 10 page paper on Classic Blast.  Send me an address &
I will send you a
>    copy.
>    Jim Deardorff
>
>
>
>
>
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