Weathering steel
Weathering steel (also known by the trademark COR-TEN steel) is a form of high-strength, low alloy steel originally developed in the 1930's by United States Steel. It is a steel alloy, chemically composed to form a stable rust-like appearance that can resist corrosion and abrasion, by forming a protective surface layer, or patina.
The protective layer’s increased resistance is produced by the alloying elements and their particular distribution and concentration. When subjected to the influence of the weather, the protective surface layer continuously develops and regenerates, allowing the rust to form.
Weathering steel is often used in external sculptures, the most iconic of which is the Angel of the North in Gateshead. It can be used in bridges and other large structural applications, such as the New River Gorge Bridge, and it is becoming an increasingly popular design choice for buildings, often used alongside materials such as glass and terracotta. An example of such a building is the distinctive Broadcasting Tower in Leeds (see top image).
The advantages of weathering steel are that because it is already weathered and ‘rusted’, there are very low maintenance costs, it can be installed easily, and the need for a protective paint system is removed. Studies have found that bridges fabricated from unpainted weathering steel can achieve a design life of 120 years with only nominal maintenance, due to the low corrosion rate.
However, there are several challenges to weathering steel. It is unsuitable for use in marine or coastal environments, and in humid subtropical climates the patina may continue to corrode instead of stabilising into a protective layer. In addition, interface details require careful design as run-off water from wet rusted steel may negatively impact on other materials, such as staining glass. This is a particular problem in the first years after installation.
Special welding techniques or materials may be needed to ensure that weld-points weather at the same rate as the other materials.
[edit] Related articles on Designing Buildings
Featured articles and news
Plumbing and heating for sustainability in new properties
Technical Engineer runs through changes in regulations, innovations in materials, and product systems.
Awareness of the Carbon Border Adjustment Mechanism
What CBAM is and what to do about it.
The new towns and strategic environmental assessments
12 locations of the New Towns Taskforce reduced to 7 within the new towns draft programme and open consultation.
Buildings that changed the future of architecture. Book review.
The Sustainability Pathfinder© Handbook
Built environment agency launches free Pathfinder© tool to help businesses progress sustainability strategies.
Government outcome to the late payment consultation, ECA reacts.
IHBC 2025 Gus Astley Student Award winners
Work on the role of hewing in UK historic conservation a win for Jack Parker of Oxford Brookes University.
Future Homes Building Standards and plug-in solar
Parts F and L amendments, the availability of solar panels and industry responses.
How later living housing can help solve the housing crisis
Unlocking homes, unlocking lives.
Preparing safety case reports for HRBs under the BSA
A new practical guide to preparing structural inputs for safety cases and safety case reports published by IStructE.
Male construction workers and prostate cancer
CIOB and Prostate Cancer UK encourage awareness of prostate cancer risks, and what to do about it.
The changed R&D tax landscape for Architects
Specialist gives a recap on tax changes for Research and Development, via the ACA newsletter.
Structured product data as a competitive advantage
NBS explain why accessible product data that works across digital systems is key.
Welsh retrofit workforce assessment
Welsh Government report confirms Wales faces major electrical skills shortage, warns ECA.
A now architectural practice looks back at its concept project for a sustainable oceanic settlement 25 years on.
Copyright and Artificial Intelligence
Government report and back track on copyright opt out for AI training but no clear preferred alternative as yet.
Embedding AI tools into architectural education
Beyond the render: LMU share how student led research is shaping the future of visualisation workflows.
Why document control still fails UK construction projects
A Chartered Quantity Surveyor explains what needs to change and how.
Inspiration for a new 2026 wave of Irish construction professionals.
New planning reforms and Warm Homes Bill
Take centre stage at UK Construction Week London.