Chris Stanley on tue 5 jan 10
ine and it sure is not. I have some serious flaking
What the Chemist says......
-----Original Message-----
From: J. Michael Robinson [mailto:robinson_m@utpb.edu]
Sent: Tuesday, January 05, 2010 11:17 AM
To: Chris Stanley
Subject: Re: FW: PETER PUGGER: I was assured that porcelain use would be
fine and it sure is not. I have some serious flaking
cHRIS:
wITH LACK OF DETAILS, THIS COULD BE DUE TO SEVERAL REASONS.
Kaolin and especially (coal mine) clays are terrific "ion exchange"
materials. Air induced corrosion when wet/in water? may in part be
due to Al reacting because it is a highly reactive metal. Al can be
dissolved in base (high pH solutions). Perhaps even mild base with
air water contact (rim around the interface??? ) with time could be
another explanation? What is the pH of any solution? What is the time
of contact? And similar info might help detail how this is done.
beaker test? Place a piece of Al in a glass beaker with the solution
only covering lower half (like a stirring rod)? and watch what
happens in a day or two? Iron really rusts, so what happens to Al?
Probably the same thing (corrosion). The Al goes into solution and
the Al+3 ions replace some of the H+ ions in the clays. These ion
exchangers (clays) may act as buffers in part and thus may not
develop a high or low pH, but check the pH before and after such tests.
Mike
At 10:37 AM 1/5/2010, you wrote:
>Ok folks...what in a standard porcelain formula would cause excessive
>corrosion on a metal tube. Normally porcelain would look like:
>Kaolin
>Ball Clay (Stuff that comes out of coal mines :-)
>Flint (ground up sand)
>Feldspar Potash, or Soda
>
>I always wondered why we kept Chemists around here......now, get to
>work....on something important;-)
>
>
>
>-----Original Message-----
>From: Clayart [mailto:Clayart@LSV.CERAMICS.ORG] On Behalf Of celia hirsh
>Sent: Tuesday, January 05, 2010 7:48 AM
>To: Clayart@LSV.CERAMICS.ORG
>Subject: Re: PETER PUGGER: I was assured that porcelain use would be fine
>and it sure is not. I have some serious flaking
>
>Hi Roxanne,
>you have my full sympathies for this frustrating situation. You should
>check the ClayArt archives for the last twelve months, since this is a
>discussion that has occurred sporadically, but without a perfect
>solution.
>
>So far, no one has determined what, exactly, is making this happen.
>Although it was suggested that it's due to the alkalinity in
>porcelain, it was only conjecture.Tests have revealed this to be
>erroneous as the alkalinity level in most porcelains is the same as
>stoneware. So you can stop the ridiculous and illogical business of
>adding epsom salts.
>
>An engineer I spoke with believes the corrosion to be due to the
>incredibly low quality of the aluminum being produced, but, who knows?
>
>I had the same problem with my Bailey. As a possible solution, Jim
>Bailey has lined my pug mill with a stainless steel liner and as soon
>as I get it back across the border, I'll let you know whether this is
>a viable solution.
>
>Have you spoken to Peter Pugger directly? The last time this
>conversation arose on ClayArt, I received a long email from them
>defending the quality of their product and affirming that they stand
>behind what they sell.
>
>Let us know what they offer to do for you.
>Good luck,
>
>Celia Hirsh
>www.hirshpottery.com
J. Michael Robinson, Ph.D.
Ellen & Bill Noel Distinguished Professor for Energy Research
and Chemistry Chair
432-552-2237 (FAX) -2236 robinson_m@utpb.edu
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