What is corten steel? Weathering steel prices, uses, benefits, alternatives
Corten steel, also known as weathering steel, is a special type of steel often used in construction, architecture, and landscape design. It’s resistant to corrosion and has strong tensile strength.Â
Here, we’ll explore what corten steel is, its unique properties and appearance, its pros and cons, and also discuss the prices of corten steel sheets and plates.
When discussing steel alloys, corten steel (also known as COR-TEN steel, though it’s a discontinued trademark in the US) or weathering steel is essential to mention. Unlike regular steel that needs painting to prevent corrosion and rust, corten steel naturally develops a protective rust-like layer when exposed to the weather. This unique quality not only adds to its durability but also eliminates the need for painting. Its rugged, rusted appearance makes it a popular choice for outdoor construction and architectural projects.
Let’s go deeper into the meaning of corten or weathering steel, its uses, key properties, manufacturing process, applications like corten steel cladding, availability of corten steel plates and sheets, prices in India, and more.
What is corten steel?
Corten steel, also known as weathering steel, is a type of steel designed to resist corrosion and maintain its tensile strength. The name COR-TEN reflects its key features: corrosion resistance and steel strength.
This alloy was developed to reduce the need for primers, paints, and coatings on steel, saving both time and costs. When exposed to the elements, corten steel forms a protective layer called patina, which prevents rusting and corrosion over time.
Due to its unique composition, corten steel is well-suited for various applications like bridges, railcars, outdoor sculptures, panels, and installations.
Why is it called corten?
The term “corten” is used to refer to corten steel or weathering steel, which is a special type of alloy steel known for its corrosion resistance and unique rust-like appearance.
However, it’s important to note that “CORTEN” or “COR-TEN” is a trademarked product of US Steel, which is no longer available as they sold their discrete plate business. Instead, what you can purchase now are steel products with ASTM finishes such as A242, A606-6, A588, and A847.
What is special about corten steel?
Corten steel stands out for its ability to resist atmospheric moisture, unlike regular steel. Its unique property allows corten steel to withstand corrosion and maintain its structural strength over time. While it develops an external patina, the steel underneath remains protected, leading to long-lasting durability.
This characteristic makes corten steel both cost-effective and sustainable, particularly suitable for structures exposed to coastal or marine environments.
Corten Steel Texture
Corten steel has a distinctive rust-like texture and typically exhibits a brownish-orange color. It develops an oxidized layer called patina as it matures, usually within 6 months to 1 year of exposure to the elements. Over time, structures made of corten steel change color as they continue to be exposed to atmospheric conditions.
The texture of corten steel is slightly rough and coarse, contributing to its unique appearance. Additionally, the coloration is uneven across the surface, varying based on the extent of exposure to the atmosphere for each part of the structure.
Is corten steel rust proof?
Corten steel is designed to be highly resistant to corrosion and rust due to its unique composition. When exposed to atmospheric humidity, it forms an oxidized layer or patina that acts as a protective barrier, shielding the inner steel from corrosion and rusting.
While corten steel is not entirely rust-proof, the protective patina layer significantly slows down the rusting process, keeping the steel relatively rust-free for many years. However, prolonged exposure to moisture or saline environments can eventually lead to the formation of rust on corten steel surfaces.
What color is corten steel?
What are the different types of corten steel?
While corten steel is not entirely rust-proof, the protective patina layer significantly slows down the rusting process, keeping the steel relatively rust-free for many years. However, prolonged exposure to moisture or saline environments can eventually lead to the formation of rust on corten steel surfaces.
What are the different types of corten steel?
Corten steel primarily comes in two main types: Corten A and Corten B, each designed for specific environments and purposes.
- Corten A: Known for its high resistance to weather conditions, Corten A is suitable for outdoor use where it can withstand harsh atmospheric elements.
- Corten B: This type is renowned for its heavy load-bearing capacity, making it ideal for applications requiring structural strength under significant loads.
Additionally, corten steel is available in different forms, including:
- Corten steel plates: These plates are thick and robust, commonly used in heavy engineering projects. They are designed to withstand severe weather conditions without corrosion, making them suitable for outdoor structures.
- Corten steel sheets: Thinner and more flexible than plates, corten steel sheets are often used in architectural applications and artistic designs. They offer versatility and are popular for their aesthetic appeal.
Both corten steel plates and sheets contribute to the distinctive appearance and durability of corten steel in various construction and design projects.
Chemical Composition of Corten Steel
| Content, % (ladle analysis) | ||||||||||
|---|---|---|---|---|---|---|---|---|---|---|
| C (max) | Si | Mn | P | S (max) | Al | V | Cu | Cr | Ni (max) | |
| Corten A | 0.12 | 0.25–0.75 | 0.20–0.50 | 0.07–0.15 | 0.030 | 0.015–0.06 | – | 0.25–0.55 | 0.50–1.25 | 0.65 |
| Corten B | 0.19 | 0.30–0.65 | 0.80–1.25 | 0.035 max. | 0.030 | 0.020–0.06 | 0.02–0.10 | 0.25–0.40 | 0.40–0.65 | 0.40 |
Mechanical Properties and Thickness Ranges for Corten Steel
| Thickness (mm) Strip Products | Plate Products | Yield strength minimum | Tensile stength minimum | Elongation miniumum | |
|---|---|---|---|---|---|
| Corten A | 2 – 12 | 6 – 12 | 345 | 485 | 20 |
| Corten B | 2 – 13 | 6 – 40 | 345 | 485 | 19 |
Corten Grades & Equivalents
| Corten | EN 10025-5:2004 |
|---|---|
| Corten A | S355 J0WP |
| Corten B | S355 J0W & S355 J2W |
Formability of Corten Steel
| Thickness (mm) | ||||||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|
| (2)–3 | (3)–4 | (4)–5 | (5)–6 | (6)–7 | (7)–8 | (8)–10 | (10)–12 | (12)–14 | (14)–16 | (16)–18 | (18)–20 | |
| Smallest allowable internal bending radius mm | ||||||||||||
| Corten A | 6 | 8 | 10 | 12 | 21 | 24 | 30 | 36 | 42 | – | – | – |
| Corten B | 6 | 8 | 10 | 12 | 21 | 24 | 30 | 36 | 42 | 48 | 54 | 60 |
Heat Treatment of Corten Steel
| Heat Treatment | Temperature °C | Treatment Time Manner of cooling |
|---|---|---|
| Stress relieving | 500–600 (target 580) | 2 minutes / millimetre thickness, minimum 30 minutes Slow cooling in the furnace |
| Normalising | 860–940 (target 910) | 1 minute / millimetre thickness, minimum 15 minutes Free cooling in air atmosphere outside the oven |
Features of corten steel
- Rust and corrosion resistance: Corten steel is naturally resistant to rust and corrosion without needing a coating. It forms a self-protective layer over time, reducing maintenance costs and offering superior durability compared to regular steel.
- Weldability: Corten steel has good weldability due to its lower carbon content, allowing for easy welding, shearing, folding, and drilling. However, welding corten steel requires specialized techniques and expertise.
- Mechanical and chemical properties: The mechanical properties of corten steel depend on factors like thickness and alloy composition. It contains various elements such as carbon, silicon, manganese, phosphorous, sulfur, chromium, copper, vanadium, and nickel, contributing to its unique properties and strength.
What is the strength of corten steel?
| Property | Description | Value or % |
|---|---|---|
| Tensile strength | High and can withstand significant stress without deformation | 470 – 630 MPa |
| Yield strength | Strong and can maintain structural integrity and its original shape under stress | 310 – 345 MPa |
| Elongation | Excellent and forms an external oxidised layer or platina to protect from rust and corrosion | 6 – 12 months for initial layer of platina |
| Corrosion resistance | High and allows the steel to stretch without breakage | ~20% |
Uses of Corten Steel
1. Roofing solutions
Corrugated roof sheets and stainless steel roofing sheets are often considered alternatives to corten steel. While they may not offer identical results in terms of cost and appearance, ASTM A606-4 and A588 are sometimes used as substitutes for corten steel in roofing applications.
2. Bridges and marine transport
In structures near water bodies like bridges and marine transport containers, corrosion and rust-resistant steel is essential. While TMT bars are commonly used for bridge construction, corten steel serves as a viable alternative due to its corrosion resistance. Intermodal shipping containers also often use corten steel for its durability. Notably, corten steel was utilized in constructing the New River Gorge Bridge in the U.S.
3. Sculptures and landscape design
Corten steel finds artistic applications in sculptures, landscape design, and outdoor furniture. It’s used for flower planters, garden borders, and artistic installations to add a decorative touch to garden areas.Â
Outdoor sculptures made from corten steel are durable and exhibit a natural rust finish, enhancing their aesthetic appeal and longevity. Additionally, corten steel is used in cladding and paneling to enhance aesthetics while providing strength, celebrating its natural properties and rust finish.
4. Laser cut corten steel signs
Corten steel is also utilized in crafting laser-cut signposts. While traditional steel is commonly used for this purpose, corten steel signposts stand out due to their aesthetic appeal, durability, and sturdiness, lasting longer than ordinary steel.
Overall, corten steel finds extensive use in architecture, construction, metal creative arts projects, and various other sectors due to its unique properties and visual appeal.
What are the alternatives to corten steel?
When considering alternatives to corten steel for a project, several options are available:
- Other forms of weathering steel: Examples include S355JOWP, which is comparable to Corten A, and S355JOW, which is similar to Corten B.
- Aluminum: While not a direct substitute for corten steel, aluminum is another corrosion-resistant metal that can be used in certain applications.
- Coated or painted steel: Stainless steel and carbon steel with coatings or paint can provide similar corrosion resistance to corten steel in specific situations.
What is the difference between corten steel and regular steel?
We understand by now that there are some prominent differences between corten steel and regular steel. These distinctions are what makes each steel type unique and suitable for specific applications.
Listed below are the main differences between corten steel and standard steel.
| Parameter | Regular steel | Corten steel |
|---|---|---|
| Appearance | Standard silvery / grey steel look, requires painting to give it a finished look | Develops a brown-orange rust like inconsistent appearance over time |
| Corrosion resistance | Requires paint, coating and specific treatment or alloy to resist corrosion and rust (e.g., stainless steel, galvanised steel ) | Highly resistant to rust and corrosion due to protective platina layer |
| Tolerance to harsh environment | Less resistant and requires specific treatment to battle moisture, heat, saline and other environmental elements | Specifically manufactured to withstand harsh weather (especially atmospheric moisture) |
| Maintenance | Requires timely maintenance (e.g., cleaning, painting, etc.) | Low maintenance as it is built for durability |
| Lifespan | May degrade sooner if not well maintained | Can last longer with basic maintenance in suitable environments |
| Recyclability | Highly recyclable (Also read: Steel recycling ) | Also easy to recycle |
| Price | Varied price range based on type and grade (standard steel is less expensive) | More expensive based on alloy composition |
What are the pros and cons of corten?
Corten steel is praised for its strength and attractive appearance, making it a favored choice. Its notable features include high tensile strength and resistance to rust and corrosion. However, there are further advantages and disadvantages to consider.
Advantages of corten steel:
- Longevity: Corten steel is durable and can last for years, providing long-term cost-effectiveness.
- Low maintenance: Once installed, it requires minimal upkeep due to its self-protective oxide layer.
- Aesthetic appeal: It has a naturally rustic appearance that adds an industrial contrast to natural landscapes, enhancing visual appeal.
- Easy to weld and shape: Its high tensile strength and weldability allow for shaping into diverse forms, suitable for various projects.
- Sustainable: Corten steel is easily recyclable, making it an eco-friendly material choice.
Disadvantages of corten steel:
- Higher price: Corten steel can be more costly than other metals with a similar appearance due to its alloy composition.
- Limited application: It’s not ideal for projects in humid subtropical climates where rusting can be accelerated.
- Initial rust runoff: Newly installed corten steel may produce rust runoff onto nearby surfaces until its protective patina fully develops.
- Staining issues: Corten steel can sometimes experience staining problems, especially in areas with high pollution or moisture levels.
Is corten steel expensive?
Yes, corten steel is generally more expensive than other metals due to its unique alloy composition and manufacturing process. The price of corten steel can be significantly higher, ranging from 50% to 300% more expensive than other types of steel.
Corten Steel Price
| Corten steel particulars | Price per kg* | Price per tonne* |
|---|---|---|
| Corten steel sheets (silver) | ₹95 – ₹110 per kg | ₹95,000 – ₹110,000 per tonne |
| Corten steel sheets (laser cut) | ₹745 – ₹770 per sq feet | na |
| Corten steel (decorative screen) | ₹315 – ₹350 per kg | ₹315,000 – ₹350,000 per tonne |
| Corten steel plate (5mm+) | ₹77 – ₹85 per kg | ₹77,000 – ₹85,000 per tonne |
| Corten steel coils (construction grade) | ₹50 – ₹57 per kg | ₹50,000 – ₹57,000 per tonne |
| Corten A sheets | ₹95 – ₹103 per kg | ₹95 – ₹103 per tonne |
| Corten steel cladding/ wall cladding | ₹385 – ₹450 per sq feet | na |
| Corten steel façade (power coated finish) | ₹450 – ₹500 per sq feet | na |
