Corten Steel -- Q&A, Applications, Problems

A. Hi Kim,
No, Corten is not a coating, but a type of steel. Sandblasting will not change its nature.

But Corten is not actually "rust resistant" like stainless steel -- it rusts as quickly as other steel. The magic of Corten is that the rust adheres a bit better and is not as fluffy and hygroscopic ... so once it rusts, there is at least some 'sealing' towards slowing further rusting -- the drier the climate and the more salt-free, the better.
Luck & Regards,


Ted Mooney, P.E. RET
Striving to live Aloha
finishing.com - Pine Beach, New Jersey

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.

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

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 ⇦this on eBay or Amazon [affil links] . 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.

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.

Penetrol

on eBay or

Amazon

(affil links)

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.

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.

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 ⇦this on eBay or Amazon [affil links] 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.

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 (Cor-ten A) and ASTM A588 (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!

Regards,

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 "Standard Specification for High-Strength Low-Alloy Structural Steel"
and
ASTM A606 "Standard Specification for Steel, Sheet and Strip, High-Strength, Low-Alloy, Hot-Rolled and Cold-Rolled, with Improved Atmospheric Corrosion Resistance".

A. COR-TEN IS GOOD.

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

It is around 1350 USD/MT.

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.

Regards,

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 Rust Cap ⇦this on eBay or Amazon [affil links] , 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.

Ed. note: Rustgrip was engaged to repair Aloha Stadium in a similar manner in 2003. You can google those words for updates.

Permacoat Xtreme

on eBay or

Amazon

(affil links)

Masterclear

on eBay or

Amazon

(affil links)

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 designed really "wet" rust finishes, and hope for some bite through the rust and onto the steel.

Regards,

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.

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).

Soda Blaster

on eBay or

Amazon

(affil links)

A. I AM BUILDING CUSTOM HOMES MADE OF CORTEN. WHAT WE HAVE FOUND TO GET THE WHOLE HOUSE TO RUST EQUALLY IS TO HAVE IT SODA BLASTED. IT IS LIKE SAND BLASTING, BUT USES A BAKING SODA TYPE MEDIUM. AS FOR THE INTERIOR WALL PANELS THERE IS A PRODUCT THAT DOES SEAL THE MATERIAL, BUT IT IS AN OIL BASED PRODUCT AND DOES TAKE A LONG TIME DRYING. IF YOU ARE IN NEED OF REMOVING PAINT OR GRAFFITI IS TO SODA BLAST IT ⇨
THE BLASTING WILL NOT ROUGHEN UP THE SURFACE.

A. Abrasive blasting is the way to go for an even rust finish.

I have found that the original rusting stage does produce staining but once this has been achieved the run off is minimal. The nature of corten, as I understand it, is that the oxidation layer becomes very dense and this protects the underlying material. There is not a continuation of oxidation into the material so there is no more oxides running off!

I love the dry dusty appearance of the corten and have never sealed it because I don't want to loose this. Is there any processes or materials that can seal the surface but leave the dry finish.