Design Life-Cycle

Lilly Tisza

DES 40A

Professor Cogdell 

The Raw Materials in Corten Steel and Their Role in its Life Cycle 

Corten steel is made up of a unique combination of steel alloys, primarily copper and chromium, that come together to form a natural rust layer that has high tolerability from natural elements, which is widely used throughout the world in various infrastructure and architecture (Corten Steel | Bunty LLC, 2021). Its combination of alloys creates a deliberate corrosion layer, which replaces the need for any protective coatings (Targowski and Kulowski). Due to corten steel’s chemistry, the natural stabilization of the physicochemical properties of the corrosion coating can last for many years, making it ideal for use in the open air (Targowski and Kulowski). 

 The raw materials sourced to make corten steel have an impact in all stages of its life cycle, but have the most significant impact on the raw material acquisition phase, the manufacturing phase, and the recycling and disposal phase. 

Raw Materials Acquisition 

Corten steel is essentially steel with added alloys (mainly copper and chromium) which make its anti-corrosion resistance 2 to 8 times better than common carbon steel (“Weathering Steel (Corten Steel) - an Impressive Construction Material”). These raw materials: steel, copper, and chromium all have their own acquisition methods that impact the life cycle of corten steel. 

Steel 

Sourcing steel is a long process as it is not an alloy found naturally in the earth, it has to be manufactured. “Steel is made primarily from iron ore, oxygen, and other minerals, including fuel materials that come from coal” (Baldonado). In terms of mining iron, Australia and Brazil dominate the world’s iron ore exports, each having about one-third of total exports (Gordon). It is said that “98% of mined iron ore is used to make steel,” which proves how crucial these mines are to the making of steel (Gordon). As iron is mostly sourced from these international mines, it is a truly global process in acquiring steel as after the iron ore is acquired, steel is then produced in industrial factories at a very large scale with other raw materials and sometimes from scrap steel.

Copper

The raw material acquisition of copper is done through mining - open-pit or underground as it is found near the Earth’s crust (Team). Though recycled copper also makes up a large portion of its sourcing, as copper alloys can be repurified (“Copper Mining and Processing: Processing Copper Ores”). Chile is the world’s largest copper producer in terms of mining and China is the leading producer of refined copper (Team). Even though much of today’s copper is still sourced through mining, there is a significant portion of copper that is sourced from recycled supplies. “It is estimated that such recycling supplies 50% of copper used in the copper industry” (“Copper Mining and Processing: Processing Copper Ores”). “In 2010, 770,000 metric tons of copper were recycled, at an estimated value of nearly six billion dollars” (“Copper Mining and Processing: Processing Copper Ores”). This is an amazing shift in the right direction toward a more sustainable sourcing practice as there are several harmful effects in the mining process (health hazards, unethical labor practices, etc.). 

Chromium

Chromium metal is commercially produced in the United States through the reduction of chromite ore with the presence of carbon, aluminum, or silicon, and subsequent purification (Wilbur et al.) Chromite ore, the main mineral in chromite, is mined (“Chromium - Minerals Education Coalition”). Ninety-nine percent of the world’s chromite is found in Southern Africa and Zimbabwe, making it necessary to export the metal to the U.S. (“Chromium - Minerals Education Coalition”). Geologists estimate that there are about 11 billion tons of mineable chromite ore in the world, enough to supply the current demand for hundreds of years, which is very high as it is mostly used for making stainless steel and other metal alloys (“Chromium - Minerals Education Coalition”). 

The acquisition of chromium is arguably more problematic than the acquisition of steel and copper as it is not as easily recyclable. According to the U.S. Geological Survey, only 25% of chromium is currently being recycled and reused. Also, there were some sources claiming that the making of chromium leads to toxic chemicals being inhaled - these sources claim this toxicity is most present in the hexavalent form of chromium (“Chromium (Cr) Toxicity”). 

Product Manufacturing

Corten steel, trademarked as “COR-TEN Steel” in the United States stands for COrrosion resistance and TENsile strength and has few genuine manufacturers around the world (“Corten Steel | Bunty LLC”). Much of corten steel is produced in Europe and the U.S., with one main manufacturer being SSAB, a Swedish steel manufacturing company (SSAB). There are several intricacies involved in the manufacturing of corten steel which gives it its admiral qualities. The raw materials involved play an integral role in corten steel’s manufacturing process. 

The corten steel manufacturing process begins with a blending of three primary plates of steel, which are mainly copper, chromium, and nickel—along with other alloying elements like phosphorus, silicon, and manganese (“Corten Steel”). This blending of alloys has to be done during the steel’s natural weathering process to ensure its stable layer of rust, its “patina” (“Corten Steel”). There is also very little carbon used during this process to ensure “pliability, strength, and toughness” (“Corten Steel”).  It is important to note that this process of combining the alloys is done when the alloys are in their manufactured state - which further adds to the complexity of this life stage. Focusing on the main steel alloys, copper and chromium, they require a long manufacturing process of their own before they can be included in the making of corten steel. 

Copper

To manufacture copper is to process the ore from its raw, mined state into a purified form that can be used by many industries, such as the steel industry (Bell). This process involves extraction from the raw materials, sulfide ore and oxide ore (Bell). Thankfully, “due to the high value of pure copper, a large portion of copper production now comes from recycled sources. In the US, recycled copper accounts for about 32% of the annual supply. Globally, this number is estimated to be closer to 20%” (Bell). As this shift towards recycling increases, the manufacturing of copper will become more efficient in all regards. 

Chromium

Manufacturing chromium is sadly a process that involves large-scale pollution. Manufacturing chromium usually takes place in an industrial setting through the reduction of chromite ore with carbon, aluminum, or silicon, and subsequent purification (Wilbur et al.).  “Chromate plants discharge large amounts of chromium-containing residues, dusts, and waste gasses. Chromium-containing residues create serious pollution problems that threaten groundwater, rivers, and marine areas” (Zhang et al.). This is highly problematic for the regions that manufacture chromium. There is “a green manufacturing process for chromium compounds has been developed by the Institute of Process Engineering, Chinese Academy of Science… with the design objective of eliminating pollution at the source” (Zhang et al.). This is a hopeful proposal that would decrease the negative effects of chromium manufacturing.

The Bigger Picture

The manufacturing process of corten steel is quite detailed as it depends on several raw materials and also follows a chronological process that is crucial to its patina formation. These metals and elements each have their own process in regards to their production and manufacturing, rendering the manufacturing process of corten steel extremely complex. 

The combination of the specific metals and elements results in a 1/4th inch thick sheet of corten steel that is ductile enough to be formed into almost any desired shape (“Corten Steel”). Its final product can be easily transported due to this final form. 

Transportation and Distribution

As corten steel is mostly manufactured in the U.S. and Europe, it is mostly transported via ground transportation (“What Is Corten Weathering Steel?”). Though, corten steel can also be shipped internationally which would be done via cargo ship (“RPM Blog | Steel Transportation: How Is Steel Shipped?”). The materials used in this transportation and distribution section are straightforward. Corten steel is classified as a “hot-rolled steel,” meaning it is usually transported without protection, as it forms a natural rust that protects it (“Steel Plates”). These steel sheets are packaged together with steel strapping (“Steel Plates”). Though, these sheets must be protected from chloride solutions - making their ideal transportation environment a dry one (“Steel Plates”). 

Overall, the transportation and distribution phase of corten steel is more so involved with the other life cycle focuses such as waste and energy. The materials involved in transportation are basic shipping and cargo materials. There could be a nuanced argument about the sustainability of these materials involved in the transportation process, such as if the shipping containers or steel strappings are made of recycled materials, but this would most likely differ depending on the distributor. 

 Use, Maintenance, and Reuse

The most common uses of corten steel are for architectural, sculptural, artistic, and landscape design purposes (“Corten Steel”). Its atmospheric corrosion-resisting properties given by the added copper and chromium make it ideal for use in the outdoors as this protective layer forms when it is exposed to the elements (“Corten Steel”). Not only is the material sought after for its durability and distinctive properties, but also for its rustic appearance that architects and designers have come to embrace. The material has become very popular for these reasons and has been used in many famous architectural projects like the Leeds Broadcasting Tower and the Barclays Center Sports Arena (“Famous Weathering Steel Architecture”). 

Corten steel is generally regarded as a low-maintenance material. “Due to its chemical composition, corten steel can withstand wet and moist climates and heat that would cause corrosive damage to other forms of steel”  (“Corten Steel”). This reaction of the steel with the special mix of alloys (copper and chromium) and elements can be credited for the steel’s low maintenance cost. Due to this quality, there is less cost involved in the upkeep of corten steel  (“Corten Steel”). However, there can be disadvantages to using corten steel as it is not best suited for all environments. For example, its corrosive-resistant properties can become redundant in environments with high-chlorine as well as underwater environments  (“Corten Steel”). More disadvantages are as follows: corten steel’s rust coloring may fade overtime, it must be cleaned regularly as many substances (grease, oil, cement) can interfere with its oxidation process, and it is not always compatible with other metals, causing galvanic corrosion to occur  (“Corten Steel”). Even though corten steel is categorized as low maintenance, this is only true when placed in its ideal environment. 

The reusability of corten steel is slightly confusing. Corten steel has the ability to “last upwards of a few decades to over 100 years” (“Benefits of Corten Weathering Steel”). This long lifespan adds to the sustainable aspect of corten steel. Though, this long lifespan is not guaranteed as it is dependent on the environment where the corten steel is housed. Some sources claim that corten steel is made of “ ecological materials that are 100% recyclable,” but there is little found on how often the material can be re-used (“Corten Steel”). This statement becomes foggy when considering corten steel’s alloy coating and the raw materials involved. SSAB, the Swedish manufacturing company that is licensed to manufacture corten steel, claims to be in a “circular economy,” meaning that their “ products are manufactured from raw materials, used and then discarded, to circular business models, where products or parts are repaired, re-used, returned and recycled” (---. “Hot rolled steel sheets and coils”). This blanket statement gives the impression of there being some sense to the reusability of corten steel, but it is still unclear. The next section will further explore the recyclability and disposal of corten steel. 

Final Disposal and Recycling 

Even though one may think corten steel is easily recyclable, as it is mainly steel, the reality is not as straightforward. Corten steel’s copper and chromium coating can make it more difficult to recycle. This section will further discuss the recyclability and disposal of corten steel from two different perspectives - from corten steel in its finished form and how its chemical coating may prevent recyclability.

Reusing Corten Steel as a Finished Product 

As discussed earlier, corten steel can have a very long life span. Due to this fact, corten steel structures or panels can be recycled for a new purpose. A case study from China explains how corten steel can be repurposed to construct a sustainable housing community. The sustainable houses were proposed to be made by the “reusing of [corten] steel container[s]” which the study claims to present “higher environmental benefits than recycling since there are less environmental impacts associated with product reprocessing” (Satola). The journal provides further research into how steel shipping containers can be repurposed for housing, praising the solution for its ability to reach near net-zero-energy in its usage and how the lifespan of these housing solutions can span up to 50 years as shown in a study from Canada (Satola). 

Why Corten Steel’s Alloy Coating May Prevent Widespread Recycling 

It is widely known that steel is easily recyclable. In fact, “steel is the world’s most recyclable material. It can be recycled again and again without comprising on quality and then reused and repurposed, enabling its participation in the circular economy” (“Australian Steel Institute - Sustainability”). Though, what is not considered here is the special coating on corten steel and how it may affect recycling efforts. As corten steel is ultimately steel, it can be melted down or recycled as scrap metal, but due to its chemical composition, it may only be used to produce corten steel and not other steel products such as stainless steel (“Grisverd”). While this isn’t necessarily an issue as corten steel is widely used and only increasing in demand, its alloy coating limits its potential to be repurposed for other products. Corten steel is not a case of the “plastic bottle phenomenon” - where plastic bottles can be transformed into tote bags, shoes, etc. It is a specialized steel product due to its addition of steel alloys, such as copper and chromium, which each have their own recycling capabilities. 

Recycling Copper and Chromium

As corten steel’s alloy coating is a mix of copper and chromium, it is important to briefly discuss these materials’ recyclability. For instance, copper “is one of the few materials that can be recycled repeatedly without any loss of performance” (“Copper Recycling - Copper Alliance”). On the other hand, recycling chromium is not as simple. “In developed countries, the general method of disposing of chromium-containing residue is landfilling or stacking until the hexavalent chromium is detoxified” (Zhang et al.). Chromium is generally recycled as down-graded scraps, but as these scraps are being re-manufactured there are high losses of chromium being reported (Johnson). “It is highly significant that the rate of chromium loss in downgraded scrap equals the amount in old scrap that is recycled for its chromium content” (Johnson). Chromium is a very inefficient material to recycle and is often just sent to landfills where it may become a hazard. As copper and chromium play an integral role in corten steel’s makeup, it is important to assess how their recyclability can play into corten steel’s. 

Conclusion 

Corten steel is a complex material, and its raw materials including steel and its two main alloy coating materials, copper and chromium, all have significant impacts on its cycle. The most fundamental impacts that these materials have are in the raw materials acquisition phase, the manufacturing phase, and the recycling and disposal phase. How the materials are acquired opens up the nuanced conversation about sustainability and recycling, the manufacturing process involves refining these materials in a specific way, and the recycling of corten steel is greatly affected by its alloy coating. 

Works Cited

“Australian Steel Institute - Sustainability.” Steel.org.au, 2023, www.steel.org.au/what-we-do/focus-areas/sustainability/. 

Baldonado, Felix. “The Process for Turning Raw Iron into Steel.” CastMasterEliteShop, CastMasterEliteShop, 29 June 2022, castmastereliteshop.com/blogs/news/the-process-for-turning-raw-iron-into-steel. 

Bell, Terence.“Manufacturing Process of Copper.” ThoughtCo, 2019, www.thoughtco.com/copper-production-2340114. ‌

“Benefits of Corten Weathering Steel.” Industrialmetalsupply.com, Industrial Metal Supply, 15 Jan. 2021, www.industrialmetalsupply.com/blog/rust-corten-steel#:~:text=Corten%20Steel%20and%20Rust&text=Most%20weathering%20steel%20types%20need,decades%20to%20over%20100%20years. 

“Chromium (Cr) Toxicity: What Are the Physiologic Effects of Chromium Exposure? | Environmental Medicine | ATSDR.” Cdc.gov, 9 Feb. 2021, www.atsdr.cdc.gov/csem/chromium/physiologic_effects_of_chromium_exposure.html#:~:text=When%20inhaled%2C%20chromium%20compounds%20are%20respiratory%20tract%20irritants%20and%20can,with%20Cr(VI)%20compounds .

“Chromium - Minerals Education Coalition.” Minerals Education Coalition, 30 July 2018, mineralseducationcoalition.org/minerals-database/chromium/ . 

“Corten Steel” Custom Machined, Forged, Cast & Plated Parts - Bunty LLC, 22 July 2021, buntyllc.com/corten-steel/. 

“Copper Mining and Processing: Processing Copper Ores.” Superfund, 13 July 2020, superfund.arizona.edu/resources/learning-modules-english/copper-mining-and-processing/processing-copper-ores.

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David. “Chromium Recycling.” Metallurgist & Mineral Processing Engineer, 24 Mar. 2018, www.911metallurgist.com/chromium-recycling/#:~:text=Most%20of%20the%20other%20steel,chromium%20 refractories%2C%20 particularly%20 foundry%20sands. 

“Famous Weathering Steel Architecture | AJ Marshall.” AJ Marshall, 4 Jan. 2018, ajmarshall.com/famous-buildings-corten-steel/. 

Gordon, Kevin. “1) Raw Material Mining and High-Quality Sinter for Quality Control in Steel Manufacturing.” Advancing Mining, Thermo Fisher Scientific, 26 Mar. 2019, www.thermofisher.com/blog/mining/raw-material-mining-and-quality-control-for-steel-manufacturing/. 

“Grisverd.” Grisverd, 2014, grisverd.com/en/about-us/materials/.

Guo, Yongyong, et al. "Monitoring of lead, cadmium, chromium and nickel in placenta from an e-waste recycling town in China." Science of the total environment 408.16 (2010): 3113-3117.

Johnson, Jeremiah, Laura Schewel, and T. E. Graedel. "The contemporary anthropogenic chromium cycle." Environmental science & technology 40.22 (2006): 7060-7069. 

PubChem. “Chromium | Cr (Element) - PubChem.” @Pubchem, PubChem, 2023, pubchem.ncbi.nlm.nih.gov/element/Chromium#section=History . 

“RPM Blog | Steel Transportation: How Is Steel Shipped?” RPMMoves.com, 2022, www.rpmmoves.com/blog/steel-transportation-how-is-steel-shipped.

Satola, Daniel, et al. "Comparative life cycle assessment of various energy efficiency designs of a container-based housing unit in China: A case study." Building and Environment 186 (2020): 107358.

SSAB. “COR-TEN Steel: A Natural Beauty.” SSAB Brands and Products, January 2020, https://www.ssab.com/en/brands-and-products/cor-ten/genuine. 

SSAB. “Hot rolled steel sheets and coils” Environmental Product Declaration (EDP) In accordance with ISO 14025 and EN 15804 +A1, vol 1, pp. 3. https://limtrevirnet.is/wp-content/uploads/2020/12/SSAB-EPD-Hot_rolled_steel_sheets_and_coils.pdf. 

“Steel Plates - Cargo Handbook - the World’s Largest Cargo Transport Guidelines Website.” Cargohandbook.com, 2023, www.cargohandbook.com/Steel_plates. 

Targowski, Wojciech, and Andrzej Kulowski. “Influence of the Widespread Use of Corten Plate on the Acoustics of the European Solidarity Centre Building in Gdańsk.” Buildings, vol. 11, no. 3, Mar. 2021, p. 133, https://doi.org/10.3390/buildings11030133. ‌

Team, Research. “Copper, Explained.” Global X ETFs, 20 Feb. 2018, www.globalxetfs.com/copper-explained/#:~:text=It%20is%20primarily%20mined%20through,lead%20into%20the%20earth’s%20crust. 

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Survey, Mineral Commodity Summaries, Jan. 2021, https://pubs.usgs.gov/periodicals/mcs2021/mcs2021-chromium.pdf. 

Wang, Tong, Peter Berrill, Julie B. Zimmerman, and Edgar G. Hertwich. “Copper Recycling Flow Model for the United States Economy: Impact of Scrap Quality on Potential Energy Benefit.” Environmental Science & Technology 2021 55 (8), 5485-5495 DOI: 10.1021/acs.est.0c08227. https://pubs.acs.org/doi/10.1021/acs.est.0c08227 

“Weathering Steel (Corten Steel) - an Impressive Construction Material.” Octalsteel, 2016, www.octalsteel.com/corten-weathering-steel. 

“What Is Corten Weathering Steel?” Corten.com, 2023, www.corten.com/frequently-asked-questions.html#:~:text=With%205%25%20copper%20in%20the,the%20material%20continues%20to%20patina.

Wilbur, Sharon, et al. “PRODUCTION, IMPORT/EXPORT, USE, and DISPOSAL.” Nih.gov, Agency for Toxic Substances and Disease Registry (US), Sept. 2012, www.ncbi.nlm.nih.gov/books/NBK158858/. 

Zhang, Yi, et al. “Green Manufacturing Process of Chromium Compounds.” Environmental Progress, vol. 24, no. 1, 2005, pp. 44–50, https://doi.org/10.1002/ep.10033 . 

Sandhya Pfile

Design 40A

Professor Christina Cogdell

Corten Steel Life Cycle: Energy

If one had to come up with symbols of American prosperity and pride, steel would certainly deserve a seat at the top. Despite the availability of other metal alloys, polymers, or organic materials, steel continues to be utilized in construction, medicine, and especially interior and exterior design. The production of steel dates back thousands of years, and it is a superior material thanks to its sheer strength, versatility, and availability (American Iron and Steel 2021). Since the 14th century, blast furnaces have been used in addition to coal burning in order to supply the growing demand for the product (American Iron and Steel 2021). When steel became popular in the United States, its uses as a material shifted from being purely structural to having aesthetic appeal, hence the present day availability of products like stainless steel appliances. While stainless steel’s appeal lies in its smooth, lustrous appearance, the development of a product called Corten Weathering Steel is an excellent example of the versatility of the material, as it is chemically formulated to develop a rugged patina when exposed to the outdoors (Masteel 2022). While Corten Steel is celebrated for its organic, au-naturel look, the development of the material is not without its costs, namely, the steep input of energy required to produce the material. The production process of Corten Steel, commonly known as weathering steel, is extremely energy intensive in the manufacturing process; while other stages of production such as material acquisition, transportation, recycling, and ultimately disposal of Corten steel may contribute to the energy impact of the product, the power required to reach the high melting point of steel and meet the demand for steel products and is extremely energy costly. 

The production of Corten steel starts with assembling the raw materials, and the energy associated with mining iron, heavy metals, and other relatively rare metals certainly contributes to the energy impact. Some very overlooked inputs in steel production are fossil fuels – in addition to fueling the mining equipment and the smelting furnaces, coal is even a raw ingredient in steel. Excavators that weigh over 800 tonnes (1 tonne = 1000 kg) and trucks with the capacity to carry 300 tonnes of coal are themselves powered by burning fossil fuels, and it can take over 770 kilograms of coal to produce one tonne of steel (BHP Coal 2022). Clearly, fossil fuels play a large role in any smelting operation. Within the United States, Iron ore is produced either by mining or via importation from foreign countries. In the year 2000, America imported 17.3 million tons (1 ton = 907 kg) of iron, mostly from Canada, Brazil, and Venezuela (ITP Mining 2013). Mining techniques in America include, but are not limited to, surface mining, blast mining, and underground mining (ITP Mining 2013). While the exact amount of fuel needed to conduct these mining operations varies, it is clear that the energy associated with acquiring raw iron ore is not insignificant. The same techniques apply to gather rarer metals like nickel-molybdenum, copper, and chromium. Mining for rarer metals includes the additional challenge of additional refinement before the substance is pure enough to be used. The mass of rare metals used in Corten Steel totals to under 3%, and these metals are not commonly obtainable within the United States, which necessitates an additional energy cost for transportation (Weathering Steel 2023). Once the materials needed to produce Corten Steel have been acquired, they can then be combined in the manufacturing stage where smelting begins.

The majority of the energy required to produce any steel product is consumed in the manufacturing process due to the high melting point and composition of steel, therefore making Corten Steel extremely energy-intensive. Historically, natural gas and coal have been burned so that furnaces may reach steel’s high melting point of around 1,370 degrees celsius (American Iron and Steel 2021). The 770 kilograms of coal required to produce one tonne (1000 kg) of steel referenced earlier is mostly consumed in this phase. Steel production has evolved over time in order to be more resource efficient, and the resulting techniques may actually lower the carbon footprint of steel mills. According to the American Iron and Steel Institute, blast furnaces have transitioned from using coal as an energy source to using natural gas and electricity. While natural gas is widely treated as a cleaner alternative to coal, burning it nonetheless results in CO2 emissions. Electric furnaces make up around 70% of modern American steel mills, and they use power in the form of electric current in order to raise scrap steel temperatures to the melting point. While this may seem more sustainable than traditional steel production methods, the energy from the electrical grid in America is far from clean burning. The U.S. Energy Information Administration reports that over 60% of America’s energy is derived from burning fossil fuels (EIA 2023). This source of energy for electric furnaces is an improvement compared to refining and burning coal, yet it would nonetheless be disingenuous to market the steel industry as being eco-friendly. Returning to the smelting phase, it is now that iron compounds can be purified. Magnetite, (Fe3O4), Hematite (Fe2O3), Goethite (Fe2O3.H2O), and Limonite (an umbrella term for impure Goethite) are the most common and most iron-rich substances in the USA (ITP Mining 2013). The first two are predominantly found in the Northeast, whereas the last two are found in the South. With this information, it does not come as a surprise that much of American steel production is located in these two regions. According to the American Iron and Steel Institute, processed iron can be smelted into large slabs or billets (narrow square rods) to be processed further elsewhere. In this initial stage of production, it is important to note that recycled or scrap steel is incorporated into the mixture. Once the Corten Steel has been produced, after a long process of smelting and alloying, the product may be put into action. 

While the exact location of Corten Steel distribution centers is not readily available, transporting the heavy material to its many consumers consumes energy. There is a great demand for Corten Steel products, as its use in landmarks such as the Hokkaido Centennial Memorial Tower (Nippon Steel 2019) or Israel’s Design Museum Holon (SSAB 2020) has popularized the material. With global demand, the production centers based in America and Europe surely rely on conventional international transportation methods. As mentioned earlier, the United States imports many of the raw materials for Corten Steel from overseas – this requires the use of container ships and railways for domestic transportation as well. Steam locomotives are likely the most commonly known type of transportation, but the high consumption of coal to power the train has made most railways shift towards diesel-powered engines (Diesel Technology Forum 2023). According to fuel efficiency metrics from CSX Railroad, “a typical train might haul 3,000 tons of freight 500 miles and consume approximately 3,049 gallons of diesel fuel” (CSX 2016). If this average usage is scaled to the global level, it is evident that a colossal amount of energy in the form of fossil fuels is required to meet the demand of steel consumers. While Corten Steel is a very specific type of steel, its contribution to global demand and resource consumption cannot be overlooked. Importing and distributing raw materials like iron ore, chromium, and copper needed for Corten Steel throughout the country is an energy-heavy task – but, exporting the final product to its many international customers is not the final step in Corten Steel’s product life cycle. 

Since Corten Steel is so specialized, it is not frequently recycled into other products. Thanks to its chemical properties, it can rust in a predictable and aesthetically pleasing manner, which means that there is practically no maintenance needed to keep the product looking ideal. While sealants can be used on the product’s surface, they are implemented in the production process and only serve as a method to control the extent of the weathering (Masteel 2022). Recycled steel is, however, incorporated into the production process of general steel products (American Iron and Steel 2021). Electric furnaces, as mentioned previously, are primarily used to reheat steel offcuts and scraps (EIA 2023). Because the steel can be recycled before it becomes alloyed with other metals, the amount of waste in the production phase is diminished. Another factor to consider is how steel products are renowned for their strength and durability – with these qualities, Corten Steel products are designed to last for a long time without needing replacement. If a piece of Corten Steel is discarded, it may only be manageable through the use of powerful machinery due to the weight and hardness of steel products in general. Because of this, Corten Steel manufacturers recommend that the products be used in lasting projects to minimize the amount of metal waste (Nippon Steel 2019). 

Throughout the production process of Corten Steel, the great energy demand inherent to metal smelting becomes apparent. Other stages of Corten Steel production do factor heavily into the energy cost, namely material acquisition and transportation, but stages like recycling and maintenance do not have large energy costs across the lifespan of the product. Ultimately, understanding the manufacturing process can help shed light on the utility of the product. Corten Steel is associated with organic and eco-friendly aesthetics and has a softer feeling than reflective or polished steel. A shift towards sustainable design choices is important when choosing materials for future constructions. With the large amounts of energy needed to create steel products, one might argue that the use of metals can only be considered ‘sustainable’ when thoughtfully incorporated into long-lasting constructions. 

Sources Consulted

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Brian Quicehuatl

DES 40A

for Professor Cogdell

Corten Steel Life Cycle Paper

Corten steel has become a popular material for exterior architecture, art, and farmers; thanks to its interesting properties which naturally protect the steel from weathering down. Unlike common metals (aluminum, iron, copper, or steel) corten steel is designed to naturally rust, when correctly used it develops a brown-orange color. The natural rusting properties prevent the steel from eroding, as the rust acts like a protection layer also known as patina. For this reason, it is being used more often as it requires less care and eliminates additional chemicals to prevent erosion. The Corten Steel itself is made up of a copper,chromium alloy steel, along with proportions of nickel, molybdenum, and phosphorus. Corten Steel is no longer produced in the United States of America meaning that most of the corten steel being used is shipped from overseas and are made in sheets of different thickness. Corten Steel is a well-known product used for exterior architecture, bridges, art, and planters; it is important to study its sustainability because of how popular it has become in recent architectural facades to the extreme of entire buildings covered with Corten Steel. Examining its waste products from a life cycle perspective shows that the raw material acquisition, product manufacturing, transportation, usees, and disposal contribute to the most environmental impact.

Corten steel has become a desirable material for many reasons, but primarily for its durability over regular steel. Its lifetime corrosion resistance is truly amazing and it is low alloy steel meaning that it requires little additions to produce when compared to stainless steel. The corten steel itself is composed of copper, chromium, phosphorus, silicon, and nickel. (Bupesh 2021) The addition of these alloys along with the high tensile strength of the steel has made Corten Steel a popular choice for designs that require exposed metals, especially in humid climates. When it comes to the decay of steel vs corten steel we can get a clear understanding of why corten steel is the preferred material. The material loss after ten years for Corten steel A is 30-75 μm (MicroMeters) compared to normal structural steel which has a material loss of 150-200 μm (MicroMeters) after 10 years. (Alinco Stainless and Steel Works,2023) Although Stainless steel itself has a higher tensile strength, over time rust can be a huge enemy as it weakens the material and can lead to dangerous outcomes. On the other hand, rust protects the corten steel, limiting the maintenance and chemical usage required to prevent its erosion. This natural “Patina '' layer has become a controversial topic of its own throughout the years of corten steel usage. When it rains or water begins to run off of the corten steel, the water then becomes contaminated with rust and can leave residue on the soil surrounding the Corten steel. There is still more research needed to be done to fully understand the potential harm or figuring a way to limit this reaction. Even Though Corten Steel is labeled to be Low alloy steel, it still requires a lot of energy and materials to produce and transport. Waste is bound to happen when producing Corten Steel and the way we limit the waste is important. The alloys used to produce corten steel are common elements and very minimal yet getting said alloys and purifying them is a wasteful task in itself. 

Corten steel is currently not being manufactured in the United States of America at the rate at which we are implementing it, meaning that production and transportation produce heavy waste material that is often overlooked. According to Brinkley and his article on corten steel, the company U.S. Steel is no longer manufacturing Corten steel. In the article, we read “US Steel sold the Corten business to the Indian multinational ArcelorMittal in 2003 and no longer produces any Corten” as it is cheaper to produce corten steel in India at the same rate. (Brinkley 2023) The Transportation required in bringing the corten steel to the USA is producing a lot of waste in the shape of fossil fuels. As of early 2023, there are many ways to export goods, we have aircraft, cargo ships, and vehicles. All of these make it possible for express shipping, particularly with small items. For big shipments of corten, both sea and truck transportation are required. A large cargo ship uses over 80,000 gallons of diesel a day, and it can take 3 or more days to travel from India to the United States. Semi-trucks are required to move the heavy steel to its destination, the fossil fuels only increase as heavier loads means more fuel required to get the semi-truck moving. There is plenty of materials being wasted now more than ever in fuels as steel has changed its manufacturing location. Although this is only for mass production of Corten Steel, we have to take into consideration that most usages of corten steels are for bridges, exterior building facades, and scenarios where metal has to be exposed. There is plenty of waste in the transportation part of the Corten steel Lifestyle, however, even the production of steel has its sets of wasteful practices that are not talked about enough to bring awareness to them. 

Waste in the steel industry is often overlooked, as the focus of the industry is to produce stronger steel at cheaper prices. Fotunatly the steel industry has begun to implement ways to reuse steel waste in the forms of Slag and Dust, unfortunately, there is still room for improvement as we overlook the wasteful waters that often include high levels of metals. There are two main types of wastes produced by steel that are beginning to be repurposed, the first being Steel Waste Slag. Steel Waste Slag is mainly composed of gangue (commercially valueless material in which ore is found) contents and some metal oxides, this byproduct can be repurposed however it requires the use of more energy to stabilize the materials. Once the materials are all stabilized you can then repurpose them as cement adhesives. (Hauiwei 2011) The second waste material that is beginning to be repurposed would be Steel Waste Dust. It is composed of iron elements and the mass fraction could reach more than 40%, which can be higher than some iron ores. (Hauiwei 2011) The issue with using the dust accumulated throughout the steel-making process would be that the dust structural makeup can vary. This is significant because it can affect the smelting process, ores by themselves can vary making every set of dust different. All of the other elements and metals wasted throughout the steel-making process are then leached, when unregulated this could lead to soil and water pollution causing environmental concerns. When it comes to stainless steel, one of the main concerns in waste is the Chromium element which is the most harmful. (Hauiwei 2011) It is not only a crisis of quantity but also a crisis arising from toxic ingredients, such as chromium, lead, nickel, and cadmium that could pose both occupational and environmental health threats. At the farthest extremes, leaching can lead to toxic pools of water and soil. This waste is taking into consideration all steel manufacturing not just corten steel, however, corten steel has the same manufacturing procedure with add-ons as steel. The waste produced is being produced in large amounts and daily, as we realize how important it is to take into consideration the steel's life cycle from the start to end.

When it comes to the manufacturing and sourcing of alloys, waste is produced in the shape of scraps, and fuels. Sourcing the alloys required to make the steel are constantly being mined and shipped around the globe to steel manufacturers. However, since corten steel requires additional chemicals and alloys to give it its natural rust, an additional step is now required in the process. During the smelting process of Corten steel, there is a demand of about (0.2-0.3 percent) of carbon. When it comes to Steel, depending on the grade of the stainless steel there is a carbon makeup of (0.05 up to 2.1) percent by weight. The only major difference between these two types of steel would be the waste of energy demand. We see energy being used in the mining process which is required not only to get the carbon but also the additional alloys smelted together to produce the patina layer. During the smelting process for stainless steel, they include virgin materials and recycled steel as it is a way to reuse some old steel scraps. Although it is being recycled there is still plenty of waste produced as the virgin material is still in its purest form and required energy to get it in said state. Approximately one tonne of stainless steel waste originated when producing three tonnes of stainless steel. (Huaiwei 2011) For corten steel, no recycling is possible for reuses, the chemicals and alloys added to the mix during the smelting process are harmful and can throw off the steel's properties. Sourcing new alloys such as iron takes time and the iron gathered are often combined with other alloys needing purification. Purifying iron is where the materials are wasted as they require a lot of energy and time. One of the major sources of waste in iron usage would be iron tailings. The steel industry has been growing and growing using more materials and poorly disposing of these iron tailings. (Li 2010) These tailings can be very toxic for the surrounding environment in which they are disposed of as they contain unwanted alloys by the steel industry. Overall the biggest concern with corten steel and waste has to be the afterlife and production. Some wastes are often overlooked and ignored when speaking of strong and weathering-resistant material.

 In conclusion, it is crucial that we take into consideration the waste produced by steel industries and demand a re-purpose of the sludge wastewater used to prevent further contamination of our soils. Along with this, we need to figure out a way to repurpose the iron tailings which have been overlooked since the production of iron steel began. There are many pros and cons to this product making it a tad bit better than regular steel as its life expectancy is longer than stainless steel however it still has to be maintained. To fully one up stainless steel corten steel would have to be recyclable and there needs to be a solution to the runoff water during usage of corten steel. Corten Steel has become a key product used for exterior uses especially in warm environments as it has proven durable surpassing even steel in certain cases. It is important to study its sustainability because of how popular it has become and how little research has been done on the material, especially since we have learned that it can have different reactions with climates. Examining its waste products from a life cycle perspective shows that the raw material acquisition, product manufacturing, transportation, usees, and disposal contribute to the most environmental impact.

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