Ivor and Olive Lewis on wed 27 oct 04
Dear Antoinette Badenhorst,
Aluminium is really a generic term for a lot of different alloys all
with their own particular properties, as is Stainless Steel. A
manufacturer should chose the best on for the anticipated service
conditions.
I suggest two points to consider. The first is that Aluminium Alloys
derive their corrosion resistance from a tenacious impervious layer of
oxide that forms on the surface of virgin metal. This "Skin" is
reasonably hard and protects against abrasion under normal exposure.
But the interior of a pug mill barrel it is subject to severe
abrasion. This exposes raw metal which corrodes rapidly in contact
with water, dilute acids and alkalies.
Second. In choosing a Stainless steel barrel, make sure that it is
"Stabilised Stainless Steel", that it has Titanium or Niobium in its
composition. If it is not stabilised then any welds will be subject
to corrosion. Parallel pitted track lines appear a short distance from
weld lines in metal that has been affected by the heat of welding. In
this case it will be water and acids that cause problems.
Best regards,
Ivor Lewis.
Redhill,
S. Australia.
Antoinette Badenhorst on wed 27 oct 04
Gee, it sounds to me that I am opening a huge question here. How would
one know then, since I am not sure if the pottery suppliers will know
what they sell.
Antoinette Badenhorst
105 Westwood Circle
Saltillo, MS 38866
(662) 869-1651
www.clayandcanvas.com
-----Original Message-----
From: Clayart [mailto:CLAYART@LSV.CERAMICS.ORG] On Behalf Of Ivor and
Olive Lewis
Sent: Wednesday, October 27, 2004 1:04 AM
To: CLAYART@LSV.CERAMICS.ORG
Subject: Pug MIll for Porcelain
Dear Antoinette Badenhorst,
Aluminium is really a generic term for a lot of different alloys all
with their own particular properties, as is Stainless Steel. A
manufacturer should chose the best on for the anticipated service
conditions.
I suggest two points to consider. The first is that Aluminium Alloys
derive their corrosion resistance from a tenacious impervious layer of
oxide that forms on the surface of virgin metal. This "Skin" is
reasonably hard and protects against abrasion under normal exposure.
But the interior of a pug mill barrel it is subject to severe
abrasion. This exposes raw metal which corrodes rapidly in contact
with water, dilute acids and alkalies.
Second. In choosing a Stainless steel barrel, make sure that it is
"Stabilised Stainless Steel", that it has Titanium or Niobium in its
composition. If it is not stabilised then any welds will be subject
to corrosion. Parallel pitted track lines appear a short distance from
weld lines in metal that has been affected by the heat of welding. In
this case it will be water and acids that cause problems.
Best regards,
Ivor Lewis.
Redhill,
S. Australia.
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Ivor and Olive Lewis on thu 28 oct 04
Dear Antoinette Badenhorst,
Three things to do:
1 Ask manufacturers what they are using and why, and hope to get
straight answers.
2 Read up on metals. Look in your library for books about Metallurgy.
To keep it simple start with "Metals in the Service of Man" by W.
Alexander and A. Street.
3 "Key Word" search "Aluminium Alloys", "Stainless Steel Alloys",
"Properties" and "Corrosion Resistance" via Google.
Best regards,
Ivor Lewis.
Redhill,
S. Australia.
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