What is Corten steel?

Corten steel - a special type of steel

Corten steel is alloyed steel that is given corrosion-resistant properties by the addition of copper, chromium and nickel. This alloy, a dense barrier layer of adhesive sulphates and phosphates, protects the steel so that no further corrosion occurs. Exposed to the weather, this material begins to take on a life of its own. The colours change and create new images.

The steel receives a rust-like oxidation layer. It forms a protection against further rusting. The final colour depends on temperature, humidity and the exact position of the product (vertical or horizontal). The formation of the final barrier layer takes approximately one year, depending on the climate.

Corten steel is very strong and therefore lends itself perfectly to garden, landscape and interior. It is also known as Cor-Ten or Corten.

standard page
Houtopslag Cortenstaal

Corten steel

Discover our corten steel products

Products in Corten steel

GEROBA is the place to go for standard products and custom-made products made of Corten steel. This at a fair price. The products are made for use in the garden or the public space.

The Corten steel products can be made in different plate thicknesses. For the standard products, 2 or 3 mm thick Corten steel plates are usually used. The products can be collected from our warehouse in Wommelgem or delivered by us on site.

Are you looking for inspiration for projects with Corten steel? Then take a look at this page.

Benefits of Corten steel

  • Endless possibilities
  • Ecological, because completely recyclable
  • Durability. Lasts 10 times longer than ordinary steel.
  • No extra treatment needed. No painting
  • No extra maintenance
  • Combination of strength and durability
  • Suitable for both modern and classic gardens
  • Excellent price/quality ratio
  • Can be used indoors and outdoors (garden/landscape)
  • As a supplier of quality products for garden and landscape, Geroba only uses Corten steel of quality class A

FAQ Corten steel

Weather-resistant steel and Corten steel: the same or not?

Yes, Corten steel and weatherproof steel are actually synonymous. In the 1960s, its use spread from America to Europe. Back then, it was only available under the name COR-TEN. Now it is available under different names.

COR= Corrosion resistance

TEN= Tensile strength

In summary = a material with good resistance to (atmospheric) corrosion with high strength.

Hydro pellets and Corten steel: not a good idea!

When placing a flower box in Corten steel, you must absolutely avoid it being wet all the time as this can lead to peeling. Therefore do not use substrates that retain water such as clay granules or hydro pellets (lava). Corten steel gets its protected patina layer by alternating dry and wet. By using these water-retaining materials, the planter remains continuously wet and the rusting process will not stop.

Rust stains on the terrace?

At the start of the rusting process, the Corten steel may give off rust on your terrace. We therefore recommend not placing the products on a light-coloured terrace in the initial phase. Once the oxidation process has been completed (maximum 1.5 years) you can place the product anywhere.

Should you still have rust deposits, these can be more or less successfully removed using a suitable rust remover. Success mainly depends on the agent used and the frequency and quality of cleaning.

How long does the rusting process take?

On delivery, our products often do not yet have the beautiful typical orange-brown colour. The formation of the rust layer starts after 2 to 3 weeks and is only completed after approximately 1.5 years. The change between wet and dry weather is important for the formation of the protective layer. The exact duration depends very much on the weather and the place where you place the product.

Are the Corten steel products subject to maintenance?

Corten steel is extremely durable. The rusting process ensures that a protective layer is applied to the corten steel. Your product therefore does not require any further maintenance. Oiling or painting is not necessary.

Corten steel does not require specific maintenance because it is able to restore the oxidised layer in the event that it is scratched, for example. Nevertheless, during this phase it is possible that the CORTENĀ® steel gives off iron oxide and causes red drops. It is recommended not to place the elements on transparent or porous surfaces.

Can I speed up the rusting process?

You don’t want to wait for the product to get its rusty colour? That is possible! Mix some salt with water and spray it on with a plant sprayer. Mixing vinegar with water also helps speed up the rusting process.

Can I coat the rust colour?

Throughout the rusting process, the orange-brown colour changes. At first, the colour is rather light and darkens over time. However, it is possible to coat the corten steel so that the colour is preserved. Contact us if you would like more information about this.

Salts and Corten steel: a good combination?

Dissolving cooking salt in water and spraying it on your product to speed up the rusting process is no problem. However, continuous exposure to large quantities of salt is. The use of Corten steel in an environment of 1.5 km from the coast is not recommended. Also be careful with exposure to products that contain large amounts of chlorine. Do not put chlorine in a Corten steel water element. The protective patina layer will be affected and may flake off.

Is Corten steel a sustainable product?

Corten steel is also used as a material in bridge building or shipbuilding and has a very long lifespan. Moreover, Corten steel is a pure type of steel without extra protective layers. This makes it easy to recycle again.

Can Corten steel rust through?

Yes, this is possible if the Corten steel stays wet all the time. This is why we coat our ponds, water tables and other water elements on the inside so that they will not rust through. It is also important that no water remains in the planters. For this reason, we provide drainage holes as standard. Hydro pellets must not be used either, as these ensure that the planters remain moist, which must be avoided at all costs.

Corten steel and the environment

Is Corten steel dangerous for the environment? No, Corten steel contains less than 1% copper and chrome. This is the reason for the long life span and protection of the metal. It is comparable to stainless steel. Corten steel is therefore much more ecological than regular steel.

Plain steel is also used for decorative items in the garden and can rust through after only a few months! The nickel and copper in ordinary steel can be absorbed by animals and thus have harmful effects.

Corten steel, in contrast to other types of steel, does not need any post-treatment. It does not need to be painted to protect it from corrosion. Therefore, no toxic substances are released during application and there will be no paint waste during maintenance or recycling.

Composition of Corten steel

Corten steel or weather resistant is a steel made of different alloys such as copper (Cu), chromium (Cr), nickel molybdenum (Ni Mo) and phosphorus (P). This combination makes it possible to increase resistance to corrosion by forming a self-protective layer, the patina.

The copper enrichment in Corten allows the formation of an oxidation layer on the surface. Phosphorus improves the action of copper and causes regular oxidation. In addition, the phosphorus ensures the healing” of the oxide layer when scratches occur.

The formation of the protective layer is closely related to the conditions of condensation, evaporation and stagnation of water. A humid atmosphere, the proximity of the sea, can prevent the formation of an effective protective patina. These factors influencing the rate of oxidation also influence the colour and appearance of Corten steel

The colour of Corten steel is usually orange-brown. However, the colour and appearance of the patina can vary, depending on the climatic conditions and pollutants in the air. The colour is never homogenous.

Below is a nice illustration of a corten steel fence after placement and a few months afterwards.

Gerofence Cortenstaal Schutting