Corten Steel - Natural Metal Planters

Corten steel is a generic term covering a range of different ‘weathering steels’, which have been developed to form a stable oxidised surface over time.

The specific technical properties of these different weathering steels are subtle, and the nuances have little relevance for use in landscape products. The essential point is that, in all Corten steel material variants, the evolving patina provides a warm, natural appearance, whilst protecting the underlying material from corrosion. What might appear as “rust” is, in fact, a protective surface patina blocking further corrosion. And, once that protective patina is formed, Corten steel will corrode with glacial slowness.

We summarise within the above tabs the key benefits, and considerations, when specifying Corten steel. For a more detailed analysis, click here: Corten Steel – The Facts and The Unique Benefits

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 planting schemes, both architectural, and naturalistic.

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.

With excellent technical performance, and offering great value-for-money over a longer time period, Corten steel can be used in a wide variety of landscape schemes.

High-Traffic Inner City Locations

Corten steel is ‘indestructible and lasts forever’, and never needs repainting, and is thus ideal for urban streetscape projects. Common public realm product applications include the edging around large planter perimeter beds, planters integrated with seating, and tree grilles and guards.

Corten steel’s variable surface patina is also highly forgiving of the wear-and-tear that is inevitable in the public realm. Worst-case, if [say] the planters are graffitied, then they can be sanded back to a uniform pattern, and the Corten steel will ‘self-heal’ in the natural way.

Pubs, Bars and Restaurants

For the same reasons given above, Corten steel is also a popular choice for high-traffic hospitality venues. 

Coastal Locations

Corten steel does not particularly like being submerged in sea water, as the chlorides inhibit the development of its protective layer. That said, for the vast majority of coastal locations, Corten steel is a great choice, as its longevity compares to 316-grade [aka ‘Marine-grade’] stainless steel. Plus Corten steel is a lot cheaper, and it does not suffer from ‘tea staining’, like stainless steel. 

Naturalistic Planting Schemes

Corten steel looks great in landscape schemes with an industrial aesthetic, but it is not limited to those settings. Corten Steel looks just as good with soft, romantic planting, like grasses; or with bright and bold floral schemes.  

Sculpture

Corten steel's architectural aesthetic, and extreme longevity, makes it particularly suitable for public realm sculpture, the most famous being Sir Antony Gormley's Angel of the North. More modestly, laser-cut Corten steel screens have become a popular – and inexpensive – sculptural element in private residential schemes.

Run-off

Concerns about run-off from Corten steel can be over-stated. In most 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 IOTA]. This takes 4-6 weeks, to do a really good job, and should be factored into project timelines, if at all possible.

That said, there are some sensible precautions that should be taken:

• Corten steel should NOT be placed onto a porous FFL substrate [such as travertine, sandstone / limestone or marble, or expensive hardwood decking], 
   
• Even if the substrate is non-porous, it is wise, where possible, to separate the Corten steel from the substrate. For example, on a roof terrace, Corten steel planters should be placed onto the insulation layer underneath [either on Wallbarn mini-pedestals or a drainage mat, to spread loadings], and then the FFL should be paved / decked up to the sides of the planters, ideally leaving a 5-10mm gap.

Further information can be found in this document: The Stages of Corten.