Weathering steel

Last updated
Texture of a sheet of Cor-Ten after being exposed to the elements for 5 years. The rust can form unevenly based on the composition of the metal. Rust-AH-2022.jpg
Texture of a sheet of Cor-Ten after being exposed to the elements for 5 years. The rust can form unevenly based on the composition of the metal.

Weathering steel, often referred to by the genericised trademark COR-TEN steel and sometimes written without the hyphen as corten steel, is a group of steel alloys that form a stable external layer of rust that eliminates the need for painting.

Contents

U.S. Steel (USS) holds the registered trademark on the name COR-TEN. [1] The name COR-TEN refers to the two distinguishing properties of this type of steel: corrosion resistance and tensile strength. [2] Although USS sold its discrete plate business to International Steel Group (now ArcelorMittal) in 2003, [3] it makes COR-TEN branded material in strip mill plate and sheet forms.

The original COR-TEN received the standard designation A242 (COR-TEN A) from the ASTM International standards group. Newer ASTM grades are A588 (COR-TEN B) and A606 for thin sheet. All of the alloys are in common production and use.

The surface oxidation generally takes six months to develop, although surface treatments can accelerate this to as little as one hour. [4]

History

The history of weathering steels began in the US in 1910s, when steels alloyed with different amounts of copper were exposed to the elements; the research continued into the 1920s and c. 1926 it was discovered that phosphorus content also helps with the corrosion resistance. [5]

In 1933 the United States Steel Corporation decided to commercialize the results of their studies and patented a steel with exceptional mechanical resistance, primarily for use in railroad hopper cars, for the handling of heavy bulk loads including coal, metal ores, other mineral products and grain. [6] The controlled corrosion for which this material is now best known was a welcome benefit discovered soon after, prompting USS to apply the trademarked name Cor-Ten. Because of its inherent toughness, this steel is still used extensively for bulk transport, intermodal shipping containers and bulk storage. [7]

Railroad passenger cars were also being built with Cor-Ten, albeit painted, by Pullman-Standard for the Southern Pacific from 1936, [8] continuing through commuter coaches for the Rock Island Line in 1949. [9]

Moorestown Interchange over the New Jersey Turnpike in 2015 Moorestown Interchange, New Jersey Turnpike 2015.jpg
Moorestown Interchange over the New Jersey Turnpike in 2015

In 1964, the Moorestown Interchange was built over New Jersey Turnpike at milepost 37.02. This overpass is believed to be the first highway structure application of weathering steel. [11] [10] Other states including Iowa, Ohio, and Michigan followed soon after. [12] Those were followed by University of York Footbridge in the United Kingdom in 1967. Since then, the practice of using weathering steel in bridges has expanded to many countries. [13]

Properties

Weathering refers to the chemical composition of these steels, allowing them to exhibit increased resistance to atmospheric corrosion compared to other steels. This is because the steel forms a protective layer on its surface under the influence of the weather.

The corrosion-retarding effect of the protective layer is produced by the particular distribution and concentration of alloying elements in it. It is not yet clear how exactly the patina formation differs from usual rusting, but it's established that drying of the wetted surface is necessary and that copper is the most important alloying element. [5]

The layer protecting the surface develops and regenerates continuously when subjected to the influence of the weather. In other words, the steel is allowed to rust in order to form the protective coating. [14]

Weathering steel grade chemical composition (excl. iron) by weight (%) [15]
Grade C Si Mn P S Cr Cu V Ni
ASTM A2420.120.25–0.750.20–0.500.01–0.200.0300.50–1.250.25–0.550.65
ASTM A5880.160.30–0.500.80–1.250.0300.0300.40–0.650.25–0.400.02–0.100.40

The mechanical properties of weathering steels depend on which alloy and how thick the material is. [16] [17]

ASTM A242

The original A242 alloy has a yield strength of 50 kilopounds per square inch (340  MPa ) and ultimate tensile strength of 70 ksi (480 MPa) for light-medium rolled shapes and plates up to 0.75 inches (19 mm) thick. It has yield strength of 46 ksi (320 MPa) and ultimate strength of 67 ksi (460 MPa) for medium weight rolled shapes and plates from 0.75–1 inch (19–25 mm) thick. The thickest rolled sections and plates – from 1.5–4 in (38–102 mm) thick have yield strength of 42 ksi (290 MPa) and ultimate strength of 63 ksi (430 MPa). ASTM A242 is available in Type 1 and Type 2. Both have different applications based on the thickness. Type 1 is often used in housing structures, construction industry and freight cars. [18] The Type 2 steel, which is also called Corten B, is used primarily in urban furnishing, passenger ships or cranes. [19]

ASTM A588

A588 has a yield strength of at least 50 ksi (340 MPa), and ultimate tensile strength of 70 ksi (480 MPa) for all rolled shapes and plate thicknesses up to 4 in (100 mm) thick. Plates from 4–5 in (102–127 mm) have yield strength at least 46 ksi (320 MPa) and ultimate tensile strength at least 67 ksi (460 MPa), and plates from 5–8 in (127–203 mm) thick have yield strength at least 42 ksi (290 MPa) and ultimate tensile strength at least 63 ksi (430 MPa).

Uses

Broadcasting Tower, Leeds, United Kingdom Broadcasting Tower 002.jpg
Broadcasting Tower, Leeds, United Kingdom
Abetxuko Bridge by Juan Sobrino of PEDELTA at Abetxuko, Vitoria, Spain AbetxukoBridge.jpg
Abetxuko Bridge by Juan Sobrino of PEDELTA at Abetxuko, Vitoria, Spain
Anneau by Mauro Staccioli at Louvain-la-Neuve, Belgium Belgique - Louvain-la-Neuve - IBA - Mauro Staccioli - Anneau - 02.jpg
Anneau by Mauro Staccioli at Louvain-la-Neuve, Belgium


Weathering steel - Fulcrum (1987) by Richard Serra in the Broadgate office estate, London RichardSerra Fulcrum2.jpg
Weathering steel – Fulcrum (1987) by Richard Serra in the Broadgate office estate, London

Weathering steel is popularly used in outdoor sculptures for its distressed antique appearance. One example is the large Chicago Picasso sculpture, which stands in the plaza of the Daley Center Courthouse in Chicago, which is also constructed of weathering steel. Other examples include Barnett Newman's Broken Obelisk ; several of Robert Indiana's Numbers sculptures and his original Love sculpture; numerous works by Richard Serra; the Alamo sculpture in Manhattan, NY; the Barclays Center, Brooklyn, New York; [20] the Angel of the North , Gateshead; and Ribbons , a sculpture by Pippa Hale, celebrating women in Leeds; [21] and Broadcasting Tower at Leeds Beckett University. [22]

It is also used in bridge and other large structural applications such as the New River Gorge Bridge, the second span of the Newburgh–Beacon Bridge (1980), and the creation of the Australian Centre for Contemporary Art (ACCA) and MONA.

It is very widely used in marine transportation, in the construction of intermodal containers [23] as well as visible sheet piling along recently widened sections of London's M25 motorway.

The first use of weathering steel for architectural applications was the John Deere World Headquarters in Moline, Illinois. The building was designed by architect Eero Saarinen, and completed in 1964. The main buildings of Odense University (built 1971–1976), designed by Knud Holscher and Jørgen Vesterholt, are clad in weathering steel, earning them the nickname Rustenborg (Danish for "rusty fortress"). In 1977, Robert Indiana created a Hebrew version of the Love sculpture made from weathering steel using the four-letter word ahava (אהבה, "love" in Hebrew) for the Israel Museum Art Garden in Jerusalem, Israel. In Denmark, all masts for supporting the catenary on electrified railways are made of weathering steel for aesthetic reasons.

Building for School of Architecture, part of the KTH Royal Institute of Technology Arkitekturskolan October 2015 03.jpg
Building for School of Architecture, part of the KTH Royal Institute of Technology

Weathering steel was used in 1971 for the Highliner electric cars built by the St. Louis Car Company for Illinois Central Railroad. The use of weathering steel was seen as a cost-cutting move in comparison with the contemporary railcar standard of stainless steel. A subsequent order in 1979 was built to similar specs, including weathering steel bodies, by Bombardier. The cars were painted, a standard practice for weathering steel railcars. The durability of weathering steel did not live up to expectations, with rust holes appearing in the railcars. Painting may have contributed to the problem, as painted weathering steel is no more corrosion-resistant than conventional steel, because the protective patina will not form in time to prevent corrosion over a localized area of attack such as a small paint failure. These cars were retired by 2016. [24]

Weathering steel was used to build the exterior of Barclays Center, made up of 12,000 pre-weathered steel panels engineered by ASI Limited & SHoP Construction. [25] The New York Times says of the material: "While it can look suspiciously unfinished to the casual observer, it has many fans in the world of art and architecture." [26] In 2015, a new building for the KTH Royal Institute of Technology School of Architecture was completed on its campus. The use of weathering steel helped the futuristic shapes of the facade fit in well with its much older surroundings and in 2015 it was awarded the Kasper Salin Prize. [27]

Disadvantages

Using weathering steel in construction presents several challenges. Ensuring that weld-points weather at the same rate as the other materials may require special welding techniques or material. Weathering steel is not rustproof in itself: if water is allowed to accumulate on the surface of the steel, it will experience a higher corrosion rate, so provision for drainage must be made. According to the NTSB, lack of drainage is what ultimately led to the Collapse of the Fern Hollow Bridge. Weathering steel is sensitive to humid subtropical climates, and in such environments it is possible that the protective patina may not stabilize but instead continue to corrode. For example, the former Omni Coliseum, built in 1972 in Atlanta, never stopped rusting, and eventually large holes appeared in the structure. This was a major factor in the decision to demolish it just 25 years after construction. The same thing can happen in environments laden with sea salt. Hawaii's Aloha Stadium, built in 1975, is one example of this. [28] Weathering steel's normal surface weathering can also lead to rust stains on nearby surfaces.

U.S. Steel Tower US Steel Tower in 2016.jpg
U.S. Steel Tower

The rate at which some weathering steels form the desired patina varies strongly with the presence of atmospheric pollutants which catalyze corrosion. While the process is generally successful in large urban centers, the weathering rate is much slower in more rural environments. Uris Hall, a social sciences building on Cornell University's main campus in Ithaca, a small city in Upstate New York, did not achieve the predicted surface finish on its Bethlehem Steel Mayari-R weathering steel framing within the predicted time. Rainwater runoff from the slowly rusting steel stained the numerous large windows and increased maintenance costs. [29] Corrosion without the formation of a protective layer apparently led to the need for emergency structural reinforcement and galvanizing in 1974, less than two years after opening. [30]

The U.S. Steel Tower in Pittsburgh, Pennsylvania, was constructed by U.S. Steel in part to showcase COR-TEN steel. The initial weathering of the material resulted in a discoloration, known as "bleeding" or "runoff", of the surrounding city sidewalks and nearby buildings. [31] A cleanup effort was orchestrated by the corporation once weathering was complete to clean the markings. A few of the nearby sidewalks were left uncleaned, and remain a rust color. This problem has been reduced in newer formulations of weathering steel.[ citation needed ] Staining can be prevented if the structure can be designed so that water does not drain from the steel onto concrete where stains would be visible.

See also

Related Research Articles

<span class="mw-page-title-main">Rust</span> Type of iron oxide

Rust is an iron oxide, a usually reddish-brown oxide formed by the reaction of iron and oxygen in the catalytic presence of water or air moisture. Rust consists of hydrous iron(III) oxides (Fe2O3·nH2O) and iron(III) oxide-hydroxide (FeO(OH), Fe(OH)3), and is typically associated with the corrosion of refined iron.

<span class="mw-page-title-main">Stainless steel</span> Steel alloy resistant to corrosion

Stainless steel, also known as inox, corrosion-resistant steel (CRES), and rustless steel, is an alloy of iron that is resistant to rusting and corrosion. It contains iron with chromium and other elements such as molybdenum, carbon, nickel and nitrogen depending on its specific use and cost. Stainless steel's resistance to corrosion results from the 10.5%, or more, chromium content which forms a passive film that can protect the material and self-heal in the presence of oxygen.

<span class="mw-page-title-main">Reinforced concrete</span> Concrete with rebar

Reinforced concrete, also called ferroconcrete, is a composite material in which concrete's relatively low tensile strength and ductility are compensated for by the inclusion of reinforcement having higher tensile strength or ductility. The reinforcement is usually, though not necessarily, steel reinforcing bars and is usually embedded passively in the concrete before the concrete sets. However, post-tensioning is also employed as a technique to reinforce the concrete. In terms of volume used annually, it is one of the most common engineering materials. In corrosion engineering terms, when designed correctly, the alkalinity of the concrete protects the steel rebar from corrosion.

<span class="mw-page-title-main">Rebar</span> Steel reinforcement

Rebar, known when massed as reinforcing steel or steel reinforcement, is a tension device added to concrete to form reinforced concrete and reinforced masonry structures to strengthen and aid the concrete under tension. Concrete is strong under compression, but has low tensile strength. Rebar usually consists of steel bars which significantly increase the tensile strength of the structure. Rebar surfaces feature a continuous series of ribs, lugs or indentations to promote a better bond with the concrete and reduce the risk of slippage.

<span class="mw-page-title-main">High-strength low-alloy steel</span> Type of alloy steel

High-strength low-alloy steel (HSLA) is a type of alloy steel that provides better mechanical properties or greater resistance to corrosion than carbon steel. HSLA steels vary from other steels in that they are not made to meet a specific chemical composition but rather specific mechanical properties. They have a carbon content between 0.05 and 0.25% to retain formability and weldability. Other alloying elements include up to 2.0% manganese and small quantities of copper, nickel, niobium, nitrogen, vanadium, chromium, molybdenum, titanium, calcium, rare-earth elements, or zirconium. Copper, titanium, vanadium, and niobium are added for strengthening purposes. These elements are intended to alter the microstructure of carbon steels, which is usually a ferrite-pearlite aggregate, to produce a very fine dispersion of alloy carbides in an almost pure ferrite matrix. This eliminates the toughness-reducing effect of a pearlitic volume fraction yet maintains and increases the material's strength by refining the grain size, which in the case of ferrite increases yield strength by 50% for every halving of the mean grain diameter. Precipitation strengthening plays a minor role, too. Their yield strengths can be anywhere between 250–590 megapascals (36,000–86,000 psi). Because of their higher strength and toughness HSLA steels usually require 25 to 30% more power to form, as compared to carbon steels.

<span class="mw-page-title-main">Patina</span> Change of objects surface through age and exposure

Patina is a thin layer that variously forms on the surface of copper, brass, bronze, and similar metals and metal alloys, or certain stones and wooden furniture, or any similar acquired change of a surface through age and exposure.

<span class="mw-page-title-main">Maraging steel</span> Steel known for strength and toughness

Maraging steels are steels that possess superior strength and toughness without losing ductility. Aging refers to the extended heat-treatment process. These steels are a special class of very-low-carbon ultra-high-strength steels that derive their strength from precipitation of intermetallic compounds rather than from carbon. The principal alloying metal is 15 to 25 wt% nickel. Secondary alloying metals, which include cobalt, molybdenum and titanium, are added to produce intermetallic precipitates.

<span class="mw-page-title-main">Rustproofing</span> Prevention of rusting of iron and steel objects

Rustproofing is the prevention or delay of rusting of iron and steel objects, or the permanent protection against corrosion. Typically, the protection is achieved by a process of surface finishing or treatment. Depending on mechanical wear or environmental conditions, the degradation may not be stopped completely, unless the process is periodically repeated. The term is particularly used in the automobile industry.

A514 is a particular type of high strength steel, which is quenched and tempered alloy steel, with a yield strength of 100,000 psi. The ArcelorMittal trademarked name is T-1. A514 is primarily used as a structural steel for building construction. A517 is a closely related alloy that is used for the production of high-strength pressure vessels.

A36 steel is a common structural steel alloy used in the United States. The A36 standard was established by the ASTM International. The standard was published in 1960 and has been updated several times since. Prior to 1960, the dominant standards for structural steel in North America were A7 and A9. Note that SAE/AISI A7 and A9 tool steels are not the same as the obsolete ASTM A7 and A9 structural steels.

ABS Steels are types of structural steel which are standardized by the American Bureau of Shipping for use in shipbuilding.

6061 aluminium alloy is a precipitation-hardened aluminium alloy, containing magnesium and silicon as its major alloying elements. Originally called "Alloy 61S", it was developed in 1935. It has good mechanical properties, exhibits good weldability, and is very commonly extruded. It is one of the most common alloys of aluminium for general-purpose use.

7075 aluminium alloy (AA7075) is an aluminium alloy with zinc as the primary alloying element. It has excellent mechanical properties and exhibits good ductility, high strength, toughness, and good resistance to fatigue. It is more susceptible to embrittlement than many other aluminium alloys because of microsegregation, but has significantly better corrosion resistance than the alloys from the 2000 series. It is one of the most commonly used aluminium alloys for highly stressed structural applications and has been extensively used in aircraft structural parts.

2024 aluminium alloy is an aluminium alloy, with copper as the primary alloying element. It is used in applications requiring high strength-to-weight ratio, as well as good fatigue resistance. It is weldable only through friction welding, and has average machinability. Due to poor corrosion resistance, it is often clad with aluminium or Al-1Zn for protection, although this may reduce the fatigue strength. In older systems of terminology, 2XXX series alloys were known as duralumin, and this alloy was named 24ST.

5086 aluminium alloy is an aluminium–magnesium alloy, primarily alloyed with magnesium. It is not strengthened by heat treatment, instead becoming stronger due to strain hardening, or cold mechanical working of the material.

AA 6063 is an aluminium alloy, with magnesium and silicon as the alloying elements. The standard controlling its composition is maintained by The Aluminum Association. It has generally good mechanical properties and is heat treatable and weldable. It is similar to the British aluminium alloy HE9.

ASTM A992 steel is a structural steel alloy often used in the US for steel wide-flange and I beams. Like other carbon steels, the density of ASTM A992 steel is approximately 7850 kg/m3. ASTM A992 steel has the following minimum mechanical properties, according to ASTM specification A992/A992M. Tensile yield strength, 345 MPa (50 ksi); tensile ultimate strength, 450 MPa (65 ksi); strain to rupture in a 200-mm-long test specimen, 18%; strain to rupture in a 50-mm-long test specimen, 21%.

Zeron 100 is a super duplex stainless steel developed by Rolled Alloys. The alloy has excellent corrosion resistance combined with high strength. It typically contains 25% chromium and 7% nickel and 3.6% molybdenum along with copper and tungsten additions. Zeron 100 has a 50–50 austenitic–ferritic structure. It also has greater resistance to chloride pitting, crevice corrosion and stress corrosion cracking than exhibited by the standard 300 series stainless steels.

5059 aluminium alloy is an aluminium–magnesium alloy, primarily alloyed with magnesium. It is not strengthened by heat treatment, instead becoming stronger due to strain hardening, or cold mechanical working of the material.

7068 aluminium alloy is one of the strongest commercially available aluminium alloys, with a tensile strength comparable to that of some steels. This material, also known as an aircraft alloy, is heat treatable.

References

  1. ↑ "Trademarks and Ownership". USS. Retrieved 13 June 2017.
  2. ↑ "Weathering Steel: A Guide to Corten and the A/B Equivalents, Origins & Standards". AZoM.com. 4 July 2016.
  3. ↑ Plate Products, 31 October 2003, archived from the original on 28 December 2007, retrieved 13 January 2010
  4. ↑ "Corten+ US". Corten+ | Rust accelerator. Retrieved 20 November 2021. The Corten+ treatment products form a rust in one hour
  5. 1 2 Morcillo, Manuel; Díaz, Iván; Chico, Belén; Cano, H.; de la Fuente, Daniel (1 June 2014). "Weathering steels: From empirical development to scientific design. A review" (PDF). Corrosion Science. 83: 6–31. Bibcode:2014Corro..83....6M. doi:10.1016/j.corsci.2014.03.006. hdl:10261/94988. ISSN   0010-938X.
  6. ↑ "Opificium: più luce non si può!". Archived from the original on 2008-09-07.
  7. ↑ "History Of Corten Steel Sculptures - History Of Corten Sculptures". allsteelsculpture.com.
  8. ↑ “The Sunbeams are Hustlers,” page 38 Trains magazine, January 1950
  9. ↑ “Railroad News and Editorial Comment,” Trains magazine, January 1950
  10. 1 2 Performance of Weathering Steel in Highway Bridges: A Third Phase Report (PDF). American Iron and Steel Institute. 1995. p. 5. Retrieved 1 September 2022.
  11. ↑ Nickerson, Robert L (October 1994). "Weathering Steel Bridges / A 1994 Review of Performance". Public Works. 125 (11): 49–50. ISSN   0033-3840 . Retrieved 31 August 2022.
  12. ↑ Historic Context for Louisiana Bridges, 1971-1985 (PDF). Mead & Hunt. October 2020. p. 8. Retrieved 1 September 2022.
  13. ↑ Ticaric, Peter; Steele, John; Lie, Felix. "Weathering Steel in Bridge Replacement of Rail Overbridges" (PDF). 8 Th Australian Small Bridges Conference. Retrieved 31 August 2022.
  14. ↑ Armstrong, Robert (14 April 2014). "Metal Building Materials and Corrosion". Absolute Steel. Archived from the original on 29 November 2020. Retrieved 25 September 2014.
  15. ↑ COR-TEN – Weather & Corrosion Resistant Steel: Technical Data, archived from the original on 20 January 2010, retrieved 13 January 2010.
  16. ↑ "Structural, Carbon & HSLA Steel Plate". A new vision of steel. Chapel Steel. 1987. Retrieved 24 September 2010.
  17. ↑ Manual of Steel Construction, 8th Edition Second Revised Printing. Chicago: American Institute of Steel Construction. p. Chapter 1, page 1–5.
  18. ↑ "Corten A Steel Plate, Corrosion Resistant Plates, Weathering Steel Plates, Weathering Steel". www.csteelindia.com. Retrieved 2017-08-10.
  19. ↑ "Corten B Steel Plate, Corrosion Resistant Plates, Weathering Steel Plates, Weathering Steel". www.csteelindia.com. Retrieved 2017-08-10.
  20. ↑ Elizabeth A. Harris (August 27, 2012). "Constructing a Facade Both Rugged and Rusty". The New York Times . Retrieved 10 September 2012.
  21. ↑ "Leeds: Ribbons sculpture celebrates city's inspiring women". BBC News. 2024-10-12. Retrieved 2024-10-13.
  22. ↑ Ruth Bloomfeld (November 11, 2009). "Feilden Clegg Bradley's Leeds complex completed". bdonline.co.uk. Retrieved 24 September 2010.[ permanent dead link ]
  23. ↑ "Shipping Container Homes Globally". Archived from the original on 2009-05-29. Retrieved 2009-05-24.
  24. ↑ "Photos of the South Shore Line in the Dunes region of Northern Indiana". people.ku.edu. Archived from the original on 15 October 2010. Retrieved 24 September 2010.
  25. ↑ "Barclays Center | 2012-12-16 | Architectural Record". www.architecturalrecord.com.
  26. ↑ Harris, Elizabeth (27 August 2012). "Constructing a Facade Both Rugged and Rusty". The New York Times. Retrieved 27 September 2013.
  27. ↑ "KTH arkitekturskolan – vinnare Kasper Salin-priset 2015". Sveriges Arkitekter. Archived from the original on 1 January 2024. Retrieved 16 February 2024.
  28. ↑ Arakawa, Lynda (11 May 2007). "Stadium rust to get $12.4M treatment". Honolulu Advertiser. Retrieved 25 September 2014.
  29. ↑ Olmstead, Elizabeth (2 October 1973). "'Old Rusty' Design Hikes Upkeep Costs". The Cornell Daily Sun. Ithaca, NY. Retrieved 2015-03-29.
  30. ↑ Sennet, Charles (8 May 1974). "Donor Wrote Corson to Demand 'Old Rusty' Repairs Be Secret". The Cornell Daily Sun. Ithaca, NY. Retrieved 2015-03-29.
  31. ↑ "Learn About Cor-Ten / F.A.Q". Corten.Com. Retrieved 17 October 2014.
This page is based on this Wikipedia article
Text is available under the CC BY-SA 4.0 license; additional terms may apply.
Images, videos and audio are available under their respective licenses.