Corten Steel is a 'Marmite' material, and it is also widely misunderstood. In this article, we seek to separate the fact from the fiction; and to explain exactly why Corten Steel is a material to embrace when designing and specifying landscape projects
EXECUTIVE SUMMARY
If you just need the headlines, without the detail, then the key points are:
Corten Steel encompasses a group of steels which possess exceptional corrosion resistance and tensile strength. Corten Steel is also known as a 'weathering' steel; as the steel forms a protective layer on its surface under the influence of the weather, and it does not need to be painted.
The Key Benefits of Corten Steel are:
- A characteristic aesthetic. Corten develops a variable patina of bronze, rust and copper hues – colours which act as the perfect foil for all manner of plantings schemes, both naturalistic and architectural.
- Extreme longevity. Material loss from unprotected Corten Steel takes place with glacial slowness [in Central London, 0.8mm over 40 years and 2.0 mm over 120 years].
- Low cost. For anything over a 10-year lifespan expectation, Corten Steel offers by far the best value-for-money return of all sheet metals, largely because it never needs to be painted / repainted.
- Essentially zero maintenance. Any maintenance that is deemed necessary would be for purely aesthetic – rather than functional and/or structural – considerations.
Specification Considerations include:
- Suitability. At the margin, the longevity of Corten Steel will be affected by the environment, and the aesthetic may vary slightly over time. However, for all practical landscape product purposes, Corten Steel is suitable for ALL environments, including industrial / coastal.
- Thickness:
- Corten Steel thicknesses of modest specification [2.0mm or 3.0mm] are perfectly fit-for-purpose for + 25 years longevity, in most environments / applications.
- For + 40 years longevity, an additional 1.0mm thickness should be added, to mitigate the forecast material loss.
- Corten Steel thicknesses =/> 6.0mm work out extremely expensive, and can only be commercially justified if the brief genuinely mandates + 120-year longevity.
- Run-off. Concerns about run-off from Corten Steel are often over-stated. In the vast majority of cases, run-off does not create an issue, so long as the metal has been professionally pre-weathered before supply [as is a standard service from GNEE].
- Finishing
Corten Steel should be left unfinished – not painted, not waxed, not lacquered. Any such surface finish is [i] not needed, [ii] will not be permanent, and [iii] negates the distinct USP of Corten Steel [its extraordinary corrosion resistance in its natural, exposed state].
In applications where the Corten Steel cannot maintain ideal wet / dry cycles to establish its protective surface oxide [such as the inside of planters], there is an argument to seal inside / unseen Corten Steel with a bitumen damp proof membrane. However, this is ONLY cost-justifiable where longevity expectations are genuinely + 40 years.
FAQ
What is special about Corten steel?
Corten Steel encompasses a group of steels which possess exceptional corrosion resistance and tensile strength. Corten Steel is also known as a 'weathering' steel; as the steel forms a protective layer on its surface under the influence of the weather, and it does not need to be painted.
Is Corten steel expensive?
Corten steel is more expensive due to the materials used and the specialized production process. Traditional steel rusts and is therefore a less suitable choice for outdoor applications. Polyester is cheaper than corten steel, but does not withstand temperature changes as well and can become porous over time.
Is corten steel better than stainless steel?
Unlike stainless steel, Corten Steel is a distinct type of alloy designed to weather gracefully over time, offering structural strength and an aesthetic quality that sets it apart.
How to tell if steel is Corten?
Corten Steel undergoes a gradual weathering process so that you may notice signs of ageing, such as rust accumulation and colour changes over time. These visual cues indicate that the steel is indeed Corten and not a standard steel with surface rust.
Does corten steel get hot in the sun?
Do corten planters get too hot in the summer? Steel planters have the ability to conduct heat and may feel warm to the touch after being exposed to the sun.
Company profile
Founded in 2008, Gnee (Tianjin) Supply Chain Group Co., Ltd. specializes in the global trade and processing of Corten steel products.
• We handle all kinds of Corten engineering projects, such as bridges, gardens, hotels, and facade systems.
• Compliant with ASTM, EN, and other international standards; third-party inspection supported.
• Exported to over 200 countries and regions worldwide.
• 8 subsidiaries across China and overseas, ensuring global service coverage.
Application Fields: Architecture, landscaping, gardening, cladding, and urban infrastructure.
