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    Table of Contents

    Any discussion on steel alloys is incomplete without talking about corten steel or COR-TEN steel (US trademark – product discontinued) or weathering steel. Steel is usually painted to safeguard it from steel corrosion and rust formation. With corten steel, this process is not required. Renowned for its distinct appearance, corten steel develops a rust like protective layer when exposed to atmospheric weather. This characteristic enhances its durability and eliminates the need for painting. The rugged, rust like texture, is favoured for outdoor construction and architectural projects.

    Let’s learn more about the meaning of corten or weathering steel, corten steel usage, main properties, how it is manufactured, corten steel cladding, corten steel plates and sheets, prices in India and more.

    What is corten steel?

    Let us begin with the meaning of corten steel.

    Corten steel is a form of weathering steel. The old name COR-TEN was given to highlight its two primary characteristics – corrosion resistance and tensile strength of steel.

    It is a strong steel alloy that was developed to lessen expenses and time spent on steel primers, painting and coats on steel to prevent rust and corrosion due to exposure to atmospheric elements. Over time, corten steel sheets when in contact with the elements, develops an external layer platina that keeps the steel from rusting.

    The unique composition makes corten steel ideal for applications such as bridges, railcars, and outdoor sculptures, panels and installations.

    Why is it called corten?

    The words corten and CORTEN should not be used interchangeably as they have different meanings.

    Corten steel or weathering steel is a special kind of alloy steel that is resistant to corrosion and rust. It has a unique rust-like texture and appearance.

    CORTEN or COR-TEN however is a trademarked product of US Steel.

    Corten steel today:

    COR-TEN was the registered trademark of U.S. Steel. Later it sold its discrete plate business. So, COR-TEN steel is no longer available. What you can buy is steel in ASTM finish (A242, A606-6, A588, and A847).

    What is another name for corten steel?

    Corten steel is also known as weathering steel due to its unique characteristics.

    The name originally is derived from COR-TEN which is trademarked by US Steel and highlights its two main properties – resistance to corrosion and its tensile strength.

    What is special about corten steel?

    What sets corten steel apart from regular steel is its ability to withstand atmospheric moisture. Unlike standard steel, corten steel sheets can resist corrosion and maintain its structural integrity for a long period. Though it develops an external platina the steel within stays protected and can last for long.

    This makes it corten steel cost-effective and sustainable. This is especially true for structures in coastal/marine environments.

    Also read: How to reduce corrosion in steel?

    Corten steel texture

    Corten steel has a rust-like appearance and has a brownish-orange colour. An oxidised layer called platina forms once the steel has matured, i.e., usually in 6 months to 1 year. Over months and years, the colour of any structure built with corten changes colour as it gets exposed to atmospheric elements.

    Corten steel texture or appearance is slightly rusty and coarse. Moreover, the colouring is inconsistent across the structure as it depends on the level of contact each part has with the atmosphere.

    Is corten steel rust proof?

    Corten steel is a steel alloy that has been manufactured to enhance its corrosion resistance and tensile strength. Once exposed to atmospheric humidity, an oxidised layer or platina gets formed which protect the inner steel from corrosion and rusting.

    However, it is not immune to rusting. The protective platina layer prolongs the rusting process often keeping the steel rust-free for years. However, over exposure to moisture or saline environments will create a layer of rust in time.

    Also read: Stainless steel rust – Is stainless steel rust free?

    What colour is corten steel?

    Corten steel has a brownish-orange colour because of its platina formation. However, in its original form, weathering steel has the appearance of standard steel. The platina gets formed over the months, i.e., 6 to 12 months.

    Moreover, the colour is not consistent across any corten steel plate or sheet structure since the colouring changes based on the extent of exposure.

    What are the different types of corten steel?

    Corten A and Corten B are the two most popular type of corten steel available in the market, each serving distinct environments and purposes.

    • Corten A: This type is known for its high resistance to weather conditions making it suitable for outdoor use.
    • Corten B: This type is known for its heavy load bearing capacity.

    Corten steel is also available in different forms, namely corten steel sheets and corten steel plates.

    • Corten steel plates: Commonly used in heavy engineering, these plates are thick and sturdy and can withstand severe weather conditions without corrosion. (Also read: Steel plates and its use in construction)
    • Corten steel sheets: Used mostly in architectural applications and artistic uses, these are thinner and more flexible. (Also read: What are steel sheets?)

    What are the main features of corten steel?

    In the next section we will take a look at the main features and properties of corten steel.

    1. Rust and corrosion resistant

    While there are other types of steel (e.g., stainless steel) that are also resistant to corrosion and rust, the distinguishing feature of corten steel is that it doesn’t need a coating to be rust-proof. It is self-protective.

    Quality corten steel plates or sheets can have 4x to 8x times the resistance power of ordinary steel. This helps to reduce maintenance cost of the corten steel structure.

    2. Weldability

    Weldability is impacted by the extent of carbon percentage content in steel. Since the carbon content in corten steel is less, it can easily be welded. It can be sheared, folded, and drilled.

    For example, corten steel panels are sold as milled steel to lessen any damage done during cutting, to the laser head. However, just like the process of steel fabrication requires specialists, welding corten requires special techniques, skills and machines and should be undertaken by experts.

    3. Mechanical and chemical properties

    Mechanical properties of weathering steel are based on the thickness and the alloy being used. Depending on the grade of weathering steel, the chemical composition varies.

    Some of the other materials used includes: carbon, silicon, manganese, phosphorous, sulphur, chromium, copper, vanadium and nickel.

    Also read: Mechanical properties of steel

    What is the strength of corten steel?

    The table below displays the key mechanical properties of corten steel to demonstrate its strength.

    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%

     

    What is the use of corten steel?

    In construction work, whether you are using a corten steel plate or corten steel sheet or any other, the important thing to remember is it should be considered only after proper inspection of the site has been done and it is safe and valid to use corten steel.

    Though there are corten steel equivalent material available for construction it is not uncommon to have a preference for its due to its financial advantages, low-maintenance cost, and genuine aesthetics.

    Let’s look at some of the common uses of corten steel in structures.

    1. Roofing solutions

    When it comes to building roofs and sliding walls, corrugated roof sheets and stainless streel roofing sheets are often looked at as corten steel equivalent material.

    Though the results, cost and appearance are not the same, yet in many instances ASTM A606-4 and A588 are used for this purpose.

    2. Bridges and marine transport

    When building structures with close contact to water, it’s necessary to use steel that is corrosion and rust resistant.

    Though TMT bars are popularly used to construct bridges, corten steel is a close alternative. Intermodal shipping containers often use corten steel. The metal has also been used in the construction of the New River Gorge Bridge (U.S.A.)

    3. Sculptures and landscape design

    Another application lies in places of aesthetics – flower planters, garden borders, landscape design, and outdoor sculptures and seating furniture. The steel can be used to plan and design garden areas to give it a decorative touch.

    Similarly, when it comes to outdoor sculptures, corten weathering steel is used to sculpt long-lasting decorative art sculptures. Corten steel is also used in cladding and panneling enhancing the aesthetics while providing strength. It celebrates the intrinsic properties by showcasing the natural rust finish.

    Also read: Cladding sheets – Uses, wall cladding types and more

    4. Laser cut corten steel signs

    The metal can also be used to make signposts. Though other metals, especially traditional steel is also used for the purpose, corten signposts are aesthetically appealing, lasts longer than ordinary steel, and sturdy.

    Corten steel is widely used in architecture and design, in the constructure sector, metal creative arts projects, and more.

    What steel is similar to corten steel?

    When using corten or any other steel in a project it is a good idea to be aware of its alternatives and substitutes.

    Alternatives to corten steel:

    • Other forms of weathering steel e.g., S355JOWP as equivalent to Corten A, S355JOW as equivalent to Corten B
    • Aluminium metal
    • Other types of coated and/or painted steel e.g., stainless steel, carbon steel (Also read: Difference between stainless steel and carbon steel)

    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? Advantages and Disadvantages

    Corten steel is known for its robustness and aesthetic appeal. It’s also highly popular for its main characteristics of high tensile strength and resistance to corrosion. But there are more advantages and disadvantages of corten steel. Listed below are some of the benefits and weaknesses of corten steel.

    What are the benefits of corten steel?

    Let us first understand what makes corten steel so popular among consumers, architects and business owners.

    Advantages of corten steel:

    • Longevity: It is strong, durable and lasts for years, making it cost-effective in the long run
    • Low on maintenance: Once installed, minimum invest is required to upkeep the structure due to its self-protective oxide layer
    • Aesthetic appeal: A naturally rustic look that’s striking and poses an industrial contrast to natura landscapes
    • Easy to weld and give shape: It’s high tensile strength and weldability allows for it to be shaped into diverse shapes (e.g., architectural, infrastructural, light and heavy-load projects)
    • Sustainable: Is easily recyclable making it an eco-friendly material to work with

    What are the cons of corten steel?

    Though the merits of coten steel are many, there are some areas where coten steel is not the best choice.

    Disadvantages of corten steel:

    • Higher price: More expensive than other steel/metals providing similar finish due to its alloy composition
    • Limited application: Not suitable for projects in humid subtropical climate
    • Initial rust runoff: Newly installed, it can runoff rust onto the surroundings
    • Other challenges: Can have staining issues

    Is corten steel expensive?

    Corten steel is more expensive than other metals based on its alloying elements. The final product price can be more by 50%-300% (than other 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

    *Prices are indicative and subject to change. Does not include GST, freight, packaging. Check with your steel supplier for final price.

    There are merits of using corten steel in business. Weathering steel can provide longevity, sturdiness and aesthetic appeal, but it can also increase projects costs if not planned and procured.

    As a buyer, therefore, be sure of your requirements, adhere by compliance and get the right kind of steel for your project.

    It can often be challenging for businesses to procure the right quality of steel at the right time. At Tata nexarc we can help you buy quality steel from verified sellers. We offer competitive prices, provide credit facility and doorstep delivery. Get in touch today and buy steel coils, sheets, channels and angles and effortlessly.

    *This was originally published on 8 September 2023 and has been updated on 26 April 2024 to keep content relevant, informative and up to date.

    Sohini Banerjee

    Sohini is a seasoned content writer with 12 years’ experience in developing marketing and business content across multiple formats. At Tata nexarc, she leverages her skills in crafting curated content on the Indian MSME sector, steel procurement, and logistics. In her personal time, she enjoys reading fiction and being up-to-date on trends in digital marketing and the Indian business ecosystem.