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Any discussion on steel alloys is incomplete without talking about corten steel or COR-TEN steel (US trademark – product discontinued) or simply put, weathering steel. In most cases, steel is painted to safeguard it from steel corrosion and rust formation. With corten steel, this process can be eliminated. This group of steel alloys are manufactured such that it develops a stable rust like texture and appearance once it is exposed to atmospheric weather conditions. They are therefore, often a preferred type of steel for outdoor construction 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, prices in India and more.
What is corten steel?
Let us start at the beginning – the meaning of corten steel.
Corten steel is 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 primers, painting and coats on steel to prevent rust and corrosion due to exposure to the environment. Instead, when exposed to the weather, in time, the steel develops an external layer platina that keeps the steel from rusting.
Corten steel texture:
Corten 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.
Main features of corten steel
To understand the uses and industry application of corten steel, let us first learn about its key features:
- Rust and corrosion resistant: While there are other types of steel (e.g., Fe 415 and Fe 500 TMT bars) that are also rust and corrosion resistant, the main distinguishing feature of corten 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.
- Weldability: The extent of carbon content in steel is what impacts its weldability. 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.
- Mechanical and chemical properties: Mechanical properties of weathering steel is based on the thickness and the alloy being used. Depending on the grade of weathering steel, the chemical composition varies and includes carbon, silicon, manganese, phosphorous, sulphur, chromium, copper, vanadium and nickel.
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).
Uses and Industry applications of weathering steel
In construction work, whether you are using a corten steel plate or corten steel sheet or any other, the important thig to remember is it should be considered only after proper inspection of the site has been done and its 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.
On that note, let’s look at some of the common applications and uses of corten steel in structures:
- 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.
- 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.)
- Sculptures and landscape design: Another application of the steel type 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.
- 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.
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 learn how to clean stainless steel rust and the difference between stainless steel and carbon steel)
Why work with corten steel? Advantages and Disadvantages
By now you must be familiar with the benefits of using corten steel panels, sheets and plates. However, it does have its demerits. We take a quick look at the pros and cons.
Advantages of corten weathering steel:
- Strong and lasts for years
- Low on maintenance
- Aesthetically appealing
- Easy to weld and give shape
- Suitable for architectural, infrastructural, light and heavy-load projects
Disadvantages of corten weathering steel:
- High corten steel price as compared with other steel/metals providing similar finish
- Not suitable for projects in humid subtropical climate
- The rust run-off is not always environmentally friendly (though corten is recyclable – read more about steel recycling)
- Can have staining issues
Corten steel price
As mentioned earlier, corten is more expensive than other metals and when using it, the final product price can be more by 50%-300% (than other steel). While steel price in India is different across cities and brands, it’s always recommended to check with the seller before finalising.
- Corten steel cladding / corten steel wall cladding using hot rolled technique: ₹380-₹450/sq feet
- Corten steel façade used in indoor and outdoor construction projects (power coated finish): ₹450-₹500/ sq feet
- Corten steel plate: ₹85,000 /tonne (JSW Steel)
- Corten steel laser cut screens (for cladding, garden wall etc.): ₹380-₹450 /sq ft
- Corten steel plates (5+ mm): ₹78,000 – ₹82,000 /tonne
As can be understood, 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. Also, there are alternatives to corten steel available.
As a buyer, therefore, be sure of your requirements, adhere by compliance and get the right kind of steel for your project.