Lily Krakowski on tue 24 sep 02
Before a couple of scientific souls write me off list to scold that I am so
pragmatic etc. and give me data my metalurgist granfather, and my
chemist-lurker father would have adored, let me add this.
I have in an earth-floored, never heated, very damp shed the casing from a
Norman Kiln dating probably to the late forties. I also have there the
stainless steel straps from a Skutt kiln that for some reason ended at the
dump some 25 years ago. Neither has rusted a wit.
So even though there probably is C and an Fe and an O relationship between
rust and fire scale, what I wanted to say was that rust and fire scale are
not the same thing in everyday life, and so rust treatments won't help.
Lili Krakowski
P.O. Box #1
Constableville, N.Y.
(315) 942-5916/ 397-2389
Be of good courage....
Rob Van Rens on tue 24 sep 02
Lily,
Not to scold, but to use your example to explain to others. This is a
perfect chance to help other lackleg chemist/engineer/metallugists
understand why equipment rusts.
-----Original Message-----
From: Lily Krakowski [mailto:mlkrakowski@CITLINK.NET]
Sent: Tuesday, September 24, 2002 11:26 AM
To: CLAYART@LSV.CERAMICS.ORG
Subject: rusting kilns and scoldings
>Before a couple of scientific souls write me off list to scold that I am so
>pragmatic etc. and give me data my metalurgist granfather, and my
>chemist-lurker father would have adored, let me add this.
>I have in an earth-floored, never heated, very damp shed the casing from a
>Norman Kiln dating probably to the late forties. I also have there the
>stainless steel straps from a Skutt kiln that for some reason ended at the
>dump some 25 years ago. Neither has rusted a wit.
Probably not. The kilns probably never get cooler than the earth floor,
thereby causing condensation on the surfaces, thereby creating direct
contact with free moisture, etc etc etc.
As long at the metal does not become a repository for moisture, it will
remain oxide-free.
>So even though there probably is C and an Fe and an O relationship between
>rust and fire scale, what I wanted to say was that rust and fire scale are
>not the same thing in everyday life, and so rust treatments won't help.
Actually, rust treatments will help, up to a point. Firescale, or black
iron oxide, or slag to a blacksmith, starts forming around 500 degrees F,
and most "rust-preventative" paints, like grill paint or furnace paint, will
volatize and flake off at around 700 F, regardless of manufacturer's claims.
This I know to be empirical fact from direct personal observation and
repeated testing (how I'd love to find something to keep my outdoor forge
from rusting).
So, you are right, rust treatments won't help on a kiln. I recommend
wire-brushing the rust or scale off the kiln, and brushing it with vegetable
oil (just like seasoning a pan). At around 550 degrees F, most vegetable
(not fruit or nut) oils turn into extremely stable long-chain polymers that
will seal the surface of the metal permanently, as long as you do not attack
them with detergent.
Basically, when you are seasoning a pan, or oil-treating hot iron, you are
actually slowly coating it in a primitive form of plastic.
Of course, since kiln outgasses can contain chlorine, sodium, potassium,
sulfur, etc etc etc, all of which can erode the coating and will eventually
combine with and corrode the metal underneath, you may have to renew this
coating from time to time.
The chemical content of the scale and rust from the outside of a kiln would
be interesting, to say the least. I wonder what sort of a glaze the stuff
would make...
>Lili Krakowski
Robert Van Rens, Workshop Coordinator
Otto Kroeger Associates
703-591-6284, x110 Phone
703-591-8338 Fax
www.typetalk.com
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