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topic 16945


A discussion started in 2002 but continuing through 2019

Will corten windows & doors survive salty sea air of Mauritius?



- MAURITIUS (Indian Ocean)

Corten woman by Willemine van Laarhoven, thumb
Corten Woman by sculptor Willemine van Laarhoven
(see entry of March 28, 2009)


A. Corten steel is a special steel used in architecture to give a pleasing (to some!) patina. The steel is designed to "weather" or "age" to give a coppery colour that will improve with time. It is resilient to many corrosive atmospheres. If you do not like it, I suggest you remove the patina and paint it with suitable paints.

trevor crichton
Trevor Crichton
R&D practical scientist
Chesham, Bucks, UK


A. I stumbled upon this website and found this question. Leave the Cor-ten steel alone. Let it patina. It is beautiful.

Dan O'Mara
- Minneapolis, Minnesota


A. It is a beautiful finish aesthetically. And I agree that it should be left alone. Does anyone know the life cycle of this finish and do companies warranty it?

Joeey Poitevin
Joeey Poitevin
- Jackson, Mississippi


A. Sir;

1. The Corten steel in your case should not be used for windows or doors. Corten Steel in primary used for bridge frame and structure usage.

2. if you must use Corten Steel, you need to get a prepaint or coated type, check with US Steel Construction manufacture. If you leave your Corten steel window and door as it is, it is unsightly and the value of your property will be affected because appearance is important for property value. Also in addition, over a long period, it will just become a pack rust looking, some may find it okay but I can ensure that majority of regular folks will not agree with it.

3. Corten Steel has a very good tensile strength but is not recommended for any residential usage. Anyhow, no one say you have to.

4. You should treat the Corten steel with a VOC corrosion inhibitor. Select the one that will give you the finishing that you want. Normally, a good VOC corrosion inhibitor should give me a long term protection as well as a smooth finishing.

Danis P [last name deleted for privacy by Editor]
engineering service - Ontario, Canada


A. I am a student at FSU and have been working with Corten material during class. We have a Corten sculpture here on campus and it has a nice dark purple color. It looks black from a distance. the oxide layer will not degrade, our sculpture has been up since 1980 and it still looks great.

Kenneth C [last name deleted for privacy by Editor]
Ferris State University - Big Rapids, Michigan

affil. link

April 21, 2008

A. In a previous life I have priced work for an award winning architect named Sean Godsell, who regularly specifies Corten as an exterior cladding on the houses he designs (often in coastal environments). To accelerate the corrosion process he requests that "Penetrol" be applied (commonly used as a paint thinner). It proves to be very successful. I also believe that the Corten can be later sealed for internal use, however I'm not certain of the appropriate paint to use.

David Down
construction - Melbourne, Australia

July 9, 2009

A. We are a window manufacturer that produces windows in Cor Ten steel among other materials. The engineer that says it should not be used for windows should know that it is very common in Europe where our system comes from. It is quite expensive about three time the cost of galvanized steel. Beauty is in the eyes of the beholder, I myself do not like the look but some do. It requires no maintenance.

Richard Sussman
- Port Washington, New York

July 16, 2009

A. We are a distributor of high end architectural windows. One of our products is available in Corten steel. The way we treat the finish is after fabrication it's allowed to weather for 2-3 weeks to develop the desired patina. The loose "dust" is then removed and a coat of wax sealer is hand applied giving it a very unique leather-like look. This finish lasts indefinitely. Corten if left alone will take 2-4 years to reach it's peak patina and then should remain in that state with very little change.

Bill Polinsky
steel window supplier - Bridgeport, Connecticut

A. Hi. "Corten" is a trademark of US Steel for "weathering steel", but US Steel only makes it in limited shapes anymore. When people speak of Corten, they usually just mean "weathering steel", which is described in ASTM A242 [affil. link to spec at Techstreet] (Cor-ten A) and ASTM A588 [affil. link to spec at Techstreet] (Cor-ten B).

I don't claim experience with weathering steels, but based on my reading I disagree a bit with some of the responses. Weathering steels are not resistant to salt air, both because the salt causes pitting, and because it is hygroscopic and the steel tends to stay wet, which prevents the proper patina from forming. What is beautiful and stable in Minneapolis, Jackson, and Big Rapids might be nothing but a rusty mess on an island in the Indian Ocean. Along with the many Corten successes, there have been spectacular failures; for example, Aloha Stadium in Honolulu has never stopped rusting and has required millions of dollars in rust treatments.

But because Corten's composition differs only slightly from standard hot or cold rolled steel (it is a low alloy), and from my reading, I would agree with Trevor & others and not anticipate any problem in waxing it or pretreating & painting it. Good luck!


Ted Mooney, Teds signature
Ted Mooney, P.E. - Pine Beach, New Jersey
Striving to live Aloha

SA Equivalent for Cor-ten A


Q. Does anyone know if there is an ASME or ASTM equivalent for the European material Cor-ten A?

Albert Verduyn
Boilermill - Holland


A. COR-TEN A is a U. S. Steel trademarked HSLA weathering steel with a minimum yield point of 50,000 psi and an atmospheric corrosion resistance 5 to 8 times that of carbon steel. Applicable standards are
ASTM A242 [affil. link to spec at Techstreet] Standard Specification for High-Strength Low-Alloy Structural Steel
A606-04 Standard Specification for Steel, Sheet and Strip, High-Strength, Low-Alloy, Hot-Rolled and Cold-Rolled, with Improved Atmospheric Corrosion Resistance.

Ken Vlach
- Goleta, California

contributor of the year honored Ken for his countless carefully
researched responses. He passed away May 14, 2015.
Rest in peace, Ken. Thank you for your hard work
which the finishing world continues to benefit from.

To minimize search efforts and to offer multiple viewpoints, we combined previously separate threads onto this page. Please forgive any resultant repetition, failures of chronological order, or what may look like readers disrespecting previous responses -- those other responses may not have been on the page at the time :-)

Corten for Ship Repair


Q. I work in ship repair. We need to weld double patch on corroded area of gas air heater water washing drain hood and basket casing. Can anybody help how economical if we use Corten steel? Roughly how much is Corten steel in USD per kg? Thanks

James Jimenez
- Singapore

October 9, 2010


While reading, I noticed that someone wanted information on price of Corten.

It is around 1350 USD/MT.


March 5, 2008

Q. Is Corten Steel good for manufacturing boats? Is it good in water environment if painted?

Norman Parmley
student - New Bern, North Carolina

May 19, 2011

Q. Someone asked if it was OK for making boats. No answers yet. Has anyone any thoughts on this?

Stamford Stoddard
buying a 16 metre boat - Chichester West Sussex UK

Use on interiors: does it rub off?


Q. Hello, I am a builder and my architect has specified Corten steel for use above an interior fireplace and on the face of the hearth. Once installed the steel will not be subject to any moisture. I assume I should pre-rust the steel before installation to get the corroded look that is so attractive with Corten.
My questions are:
1. Will it corrode in a dry environment?
2. If I am to pre-rust it is there any treatment I should use on the steel to remove oils or other contaminants.
3. Should I use sea water to hasten the corrosion? I have actually tried a few samples using sea water and have had varying success, some with pretty good results, others that the corrosion is very spotty, as if something present on the surface was preventing the corrosion.
4. If I achieve the desired level of corrosion before installing the pieces, can I seal it to prevent people in the house from getting the rust on them or their clothes?

Mr. Courtney G [last name deleted for privacy by Editor]
construction - Santa Cruz, California

January 31, 2008

Q. Looking for the follow up on Mr. Courtney G's interior Corten questions. I too am building and we are using Corten to clad fireplace, hearth and surrounding wall. We are looking for help in areas of thickness used, mounting, and sealing so customer won't get it on themselves.

F Heathen
- Madison, Wisconsin

February 12, 2008

Q. Should Corten steel panels rust to the point that you can rub the color off easily?

Robert Vtinreo
installer - Watertown, Minnesota

June 17, 2013

A. Hi. The rust will brush off, and the customers will get it on themselves. I think it is may be more practical to paint the steel a nice rusty color if people will be touching it. Companies which supply Corten roofing also offer painted steel in very closely matching colors. Good luck.


Ted Mooney, Teds signature
Ted Mooney, P.E. - Pine Beach, New Jersey
Striving to live Aloha


A. If you have to paint it and want it to last, wire brush off the worst till you have reached an acceptable finish level, it does not need cleaning back to perfect, then paint with Hammerite [affil. link to product info on Amazon], this is a bonding paint available in many colours.

it will last for years and should prevent further rusting.

Friends and I have used it for over 30 years and never found any problems, we have even used it to cover the bottoms of cars to delay salt corrosion, as our local authorities believe in very liberal applications of salt on our roads.

Peter Nixon
- Middlesbrough, UK

Ed. note: Rustgrip was engaged to repair Aloha Stadium in a similar manner in 2003. You can google the terms and get an update from them.

December 16, 2011 -- this entry appended to this thread by editor in lieu of spawning a duplicative thread

Q. Is it possible to stop weathered Corten from ending up on the clothes of the general public. Can it be sealed after weathering?

Tim Farrow
landscape architect - England

June 2013

A. Hi Tim. The rust will rub off. Clear coating or painting Corten should not be difficult, but a chain is only as strong as its weakest link; so, with the rust not tightly adherent to the substrate, the clear coat adhering to the rust may not be much help. I'd try a clearcoat that is really watery, and really "wets", and hope for some bite through the rust and onto the steel.


Ted Mooney, Teds signature
Ted Mooney, P.E. - Pine Beach, New Jersey
Striving to live Aloha

affil. link

affil. link

January 30, 2009

A. The Corten steel finish can be coated using a water based coating Perma Coat then finished coated with Master Clear from Modern Masters. I have seen this effect extensively used in Spain and Portugal.

neil cody
design - Vancouver, BC, Canada

Ed. note: Thanks much, Peter &Neil -- but this metal finishing site focuses on educating people in how various finishing technologies work, rather than in testimonials to brand names & the hocus-pocus of secret ingredients. As far as possible, let's try your best to talk about the technologies employed, rather than about brands (it helps us avoid drowning under spam -- no salesperson can stomach their competition being publicly praised and will always try to top it, sometimes posing as a satisfied customer). Thanks!

April 16, 2010 -- this entry appended to this thread by editor in lieu of spawning a duplicative thread

Q. Want to use container to build a house project in Thailand Bangkok.
Like to know the was brand to protect corten steel from rusting after I sandblast.

Jean Ferron
- Thailand

Does that come in Black?


Q. I am using Corten steel (6 mm thick), but would like to achieve a almost uniform black color for a special application. Does anyone knows any 'tricks' or procedures ?
thanks for any reply.

Michael P [last name deleted for privacy by Editor]
- Adelaide, South Australia


A. I work as a contractor and we have had rust stain problems with the Corten steel. I am not sure this helps with the original question, but we have used a "blued" metal with a clear powder coat finish to achieve a nice mottled, but rust free look. The "bluing" is done by hand, I believe it is the same chemical used to maintain gun barrels. (at least, that is where I first heard of it).

Colin Thompson
- Los Angeles, California

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