Not very scientific. I used to help make the stuff so this stuck in my mind. 
I think it was Chicago and I remember it was the offices of a steel company. 
It was reported that when the air pollution was reduced the rust washed off 
the Corten and stained the footwalk brown.
Peter Hutchison
----- Original Message ----- 
From: "Kinder, Joachim" <[log in to unmask]>
To: <[log in to unmask]>
Sent: Monday, February 23, 2009 1:37 PM
Subject: AW: Weathering steel (Cor-ten) conservation.



Dear Arantza,

as metallurgist I did a tiny bibliographic research in the past mainly to 
receive information about the reason of Cor-ten steel to be more or less 
corrosion-resistant. From that little research I remember that during the 
formation of rust on the surface of a corroding steel the alloyed Cu will 
form a subsurface-layer below the rust because of its noble character. 
Problematic are surfaces of sculptures etc. which are oriented horizontally. 
In this case for example rain water will pond for a while and this leads to 
a penetration of the Cu-layer thereby promoting corrosion. Because this 
bibliographic research happens in the early 90ties I do not have the old 
results available.

Some years ago I conducted a scientific research regarding the cleaning of 
old metallic surfaces which were formed during manufacturing (i.e. casting 
skulls on cast iron and hammer scale on steels). The cleaning experiments 
were done by the German company Kaercher (see: www.karcher.com) with 
blasting techniques using high water pressure or high-pressure dry-ice 
particles. Both techniques were able to clean the rusted and somewhat dirty 
surface of the testing specimen sufficiently without affecting the old oxide 
surface layer too much. But of course the rust was fully removed which 
definitely will not be your intention!

I can provide you with a little publication about my cleaning examination 
which was prepared for an international conference in Slovakia in 2006 in 
English language if you like. Perhaps it might be possible to do some 
examinations together with Kaercher but this time on dirty Cor-ten steel 
surfaces in order to find-out proper parameters for cleaning such rust 
surface without removing the wanted rusty surface too much ...

Kind regards!

Dr. Joachim Kinder

Materialprüfungsanstalt Universität Stuttgart
- Materials Testing Institute of University Stuttgart -
(MPA Stuttgart  -  Otto-Graf-Institut (FMPA))
Department 52350 - Failure Analysis in Mechanical Engineering
Pfaffenwaldring 32
D-70569 Stuttgart
Phone: +49 (0) 711 685-6 03 11
Fax: +49 (0) 711 685-6 39 01
e-mail: [log in to unmask]
Internet: http://www.mpa.uni-stuttgart.de

-----Ursprüngliche Nachricht-----
Von: Arch-Metals Group [mailto:[log in to unmask]] Im Auftrag von 
Arantza Garcia
Gesendet: Donnerstag, 19. Februar 2009 09:06
An: [log in to unmask]
Betreff: Re: Weathering steel (Cor-ten) conservation.

Hello,

Thank you very much for the bibliography suggestion.
It is a pity it is in German. I will try to get someone to translate the 
contents.

Thanks!
best

Arantza García
Dpto. de Conservación
Museo Guggenheim BILBAO
Tel: 00. 34. (9) 403 91 26 / Fax: 00.34.(9) 435 90 61
e-mail: [log in to unmask]

-----Mensaje original-----
De: Arch-Metals Group [mailto:[log in to unmask]] En nombre de 
[log in to unmask]
Enviado el: jueves, 19 de febrero de 2009 8:57
Para: [log in to unmask]
Asunto: Re: Weathering steel (Cor-ten) conservation.

here is a topic about this:

http://www.nextroom.at/publication_preview.php?picture_id=463&publication_id=799&box1_id=-1#annex



> Hello all,
>
> I would like to get in contact with professionals dealing with
> conservation and
> maintenance of weathering steel (Cor-ten steel) sculptures or
> structures
> (exhibited indoors and/or outdoors).
>
> We are currently carrying out research into the deterioration and
> conservation
> of weathering steel (Cor-ten) sculptures. An area of specific
> interest in the
> project is the problem of graffiti, (protective treatments and their
> removal)
>
> Any suggestions would be greatly appreciated.
> Thanks
>
> Best
> Arantza.








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Fundaziokoekin. Horregatik erakundeak ez du onartzen azaldutako 
informazioaren gaineko erantzukizunik.


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