CORTENFABRIKEN
Bond lampshade Corten Ø 60 cm
Flower outdoor privacy screen / fence with graphic patterns that can be LED-illuminated ~ 180 cm or 110 cm (patio privacy screen, pergola, trellis & wind protection). Welded Corten posts for a minimalist and exclusive impression.

All About Corten Steel – Material Guide, Care, and Treatment

Corten steel (COR-TEN) has become one of the most popular materials for trend-conscious individuals in gardening and interior design. With its unique, living appearance and high durability, it adds a warm and exclusive feel. Here, we gather everything you need to know about the material, how to care for it, clean it, accelerate the rust process, and protect your surfaces.

What is Corten Steel (COR-TEN)?

Corten steel is an alloyed steel created by melting together several metals. What distinguishes Corten steel from regular rusting steel is its specific content of copper, chromium, manganese, and nickel.

  • The genuine brand: U.S. Steel holds the registered trademark COR-TEN, but there are equivalent alternatives on the market today.
  • Beware of simpler steels: Simpler steel types lacking copper can also rust, but they are not as durable and will rust through much faster. Always verify the steel’s composition.
  • Applications: The material is widely used for facades, planters, sculptures, fire pits, privacy screens, and furniture. (Fun bonus fact: Corten steel is 100% recyclable and also magnetic).

Durability of Corten Steel and How to Accelerate the Rust Process

Delivery condition: Good to know is that Corten steel is delivered in an untreated, dark, or gray steel state. The beautiful rust only develops when the product is placed outdoors and exposed to the elements.

The beauty of Corten steel is that it is a living material that changes over time. The weather-resistant steel forms a thin, reddish-brown rust layer. This layer protects the metal and prevents moisture from penetrating, making the material maintenance-free and highly resistant to corrosion. It normally takes about 2 years to achieve a completely even and dark rusted surface naturally, but the process can be accelerated.

Unique outdoor table / round coffee table or fire pit / fire basket. Its graphic pattern casts a beautiful glow to enjoy with our LED lighting.
Utseende rost efter 3 års utomhusbruk.

How to accelerate the rust process on Corten steel:

  • Salt and vinegar mixture (Recommended for a reddish-brown color): Mix 2 tablespoons of salt and 2 tablespoons of vinegar in 1 liter of water in a spray bottle. Ensure all salt is completely dissolved before spraying an even layer over the entire surface. This provides a good balance between red and yellow colors. Spray only once and then leave the sheet outdoors to be exposed to changing weather. If you spray too many times, the surface will easily become powdery and uneven from rust. Rinse thoroughly when you are satisfied with the patina.
  • Salt and water mixture (For a more yellow tone): Mix 2 tablespoons of salt in 1 liter of water. Apply in the same way; this mixture often gives a slightly yellower tone initially. Rinse thoroughly when you are satisfied with the patina.
Accelerate the rust process

There are also commercial rust accelerators that provide faster results. Products like Rost Patina can be used for this, but it is easy to overdo the amount of agent. If you apply too much, the outermost layer can become pulverized and you will be forced to start over. Therefore, always follow the manufacturer’s instructions carefully.

Orchid round pattern

Tips for Using Corten Steel Outdoors

Corten steel is a durable material, but keep the following in mind for maximum lifespan and best results in the garden:

  • Material thickness: Our planters and vessels are made of 3 to 5 mm steel. For products expected to last at least 40 years in harsh environments, a steel thickness of at least 4 mm is recommended.
  • Can you grow edibles in Corten steel? Yes, it is completely safe. What leaches from the steel is iron oxide, which in small amounts acts as a micronutrient for the soil. The plants are not harmed, and your harvest is completely safe to eat.
  • Protect roots from heat: Since dark steel absorbs a lot of heat, Corten steel planters can become very hot during peak summer. To prevent plant roots from burning or drying out too quickly, we recommend insulating the inside. Line the inside with, for example, a sleeping pad, cellular plastic (Styrofoam), or thick bubble wrap before filling with soil. Our square and rectangular vessels feature a practical decorative frame that neatly hides the insulation.
  • Avoid standing water: Do not let water sit constantly against the steel. Ensure your pots have drainage holes.
  • Create a “rust trap” with decorative stones: During the first two years, the steel will “bleed” rust. To protect expensive paving stones or wooden decks from discoloration, you can place your large planters on a small bed of gravel or decorative stones. The rust water will then drip straight down into the gravel where it blends in naturally.
  • Consider your choice of screws: If the products are assembled with screws, it is crucial to use stainless steel screws (e.g., A2/A4) or screws specifically designed for Corten steel. Regular steel screws create metal-to-metal contact (galvanic corrosion) that can cause the screws to rust prematurely or leave ugly streak marks.
  • Autumn and winter care: In the autumn, brush away damp leaves and garden debris from the steel, as they can trap moisture and cause uneven discoloration. In winter, avoid spreading road salt or de-icing salt near your Corten products, as the salt breaks down the protective rust layer.
Maintenance-free privacy screen / fence / trellis in Corten with graphic patterns that can be LED-illuminated. Create privacy, pergolas & room dividers. Maintenance-free outdoor privacy screen in laser-cut metal. Various unique screens with lighting for garden privacy, wind protection, railings & indoor art. Plant supports, heat pump covers.

Cleaning Corten Steel

Keeping your products fresh is very easy. The fastest way to clean Corten steel is by going over the surface with a high-pressure washer. The water pressure effectively removes dust, soil residue, and moss.

Note: Do not hold the nozzle too close to sensitive surfaces, and be prepared that the cleaning might wash away some loose rust water.

Glow, an elegant birdbath on a pedestal in Corten for multiple uses. Also suitable as a planter bowl, fire pit, or large urn.
Once the Corten has oxidized (rusted) to your desired patina, you can seal it with CT-7571-W. A Corten sealer that prevents the Corten from continuing to rust.

Sealing and Treating Corten Steel

When Corten steel has just begun to rust and has not yet developed a solid Corten surface, it naturally sheds rust. This is especially noticeable if you pour water into a Corten bowl – during this initial period, it is therefore recommended to change the water frequently. Once the steel has built up its protective patina, the rust instead settles at the bottom of, for example, a birdbath, making the water appear much clearer. Other surfaces shed much less after two years.

If you proactively want to reduce rust runoff or protect the inside, there are three main options:

1. 2K Varnish (Permanent protection in direct contact with water)

Provides a highly durable and lasting surface that stops rust runoff completely.

Recommended products:

  • Primer: SprayMAX 2K Epoxy Primer Filler
  • Topcoat: Epifanes 2K Polyurethane Varnish (satin finish)

Note: This varnish requires protective equipment during application.

2. Natural Wax / Carnauba Wax (Requires maintenance)

Seal the rust patina with a hard, heat-resistant wax that withstands the sun, such as Carnauba wax.

  • Mix the wax: Melt the Carnauba wax in a water bath. Mix with 10–15% pure coconut oil or cold-pressed raw linseed oil to make it easier to work with. (Note: Do not use boiled linseed oil from the hardware store as it contains toxic chemical drying agents).
  • Application: Brush a thin, even layer on the inside of the bowl. Work quickly because the wax solidifies fast when removed from the heat. A thin layer is enough to create a water-repellent surface. Let it cure for a couple of days before filling with water.
  • Maintenance: Apply a new layer of wax when you notice the water starting to turn rusty again (several times a season).

3. Water-based Corten Sealer (CT-7571-W)

A professional, water-based protection that works excellently both indoors and outdoors. The sealer stops all further rust formation, is 100% waterproof, and provides strong protection against UV radiation and wear.

Note: The surface becomes darker when varnished with this. It is not recommended for birdbaths or surfaces constantly submerged in water, but is excellent for planters and facades to completely avoid rust runoff. You can find the sealer here.

Tips for Using Corten Steel Indoors

Corten steel adds a warm and exclusive tone indoors as well.

  • Avoid moisture stains: Since welding seams can let some moisture through when very wet, you should use a tight-fitting plastic inner pot with a saucer underneath.
  • Airflow: Place pots on small spacers (for example, a few coins) to aerate the surface underneath.
  • Protect surfaces: If you are worried about color shedding, place the steel on easy-to-clean surfaces like glass or tile.
  • Varnishing small pots: For smaller indoor pots, you can advantageously use a spray varnish or our water-based Corten sealer.
Glass frame & glass saucer for Corten planters. About Corten steel (COR-TEN): tips regarding material thickness, how to accelerate the rust process, household tips for rust stains & LED lighting for Corten.
Matt klarlack

How to Remove Rust Stains from Corten Steel and Other Surfaces

If you happen to get rust stains on other materials, there are simple tricks:

  • On glass: Use regular toothpaste and a dish sponge. Polish with circular motions and rinse off.
  • On stone: Sprinkle baking soda on the surface, pour on a little water, and let it sit. For tougher, dark stains, oxalic acid can be used (leave on for up to 2 days).
  • On wood: Use oxalic acid to dissolve the rust.
INSTRUCTIONAL VIDEO - REMOVE RUST
The Art Cube side table sets the perfect evening atmosphere. A unique outdoor/indoor side table with lighting. Get a small coffee table with glass. Art Cube is perfect as a lighting design for flower beds and patios, as well as for the living room. Cortenfabriken creates unique, minimalist lighting & interior design for private & public spaces. Design for gardens, patios & home decor.
Tulip garden art is a unique rusted statue made of Corten steel. This garden decoration creates a unique ornamental feature, either illuminated along a path or combined with a fountain. Create durable design online – custom furniture, garden decor, and decorations for built-in solutions & public spaces Learn all about Corten steel (COR-TEN): material thickness, the rusting process, waxing birdbaths, rust removal, and lighting tips for Corten.

Tips for Lighting Corten Steel

The right lighting transforms Corten steel into an artistic focal point even during the dark season.

  • Color temperature (Kelvin): Preferably choose 3000K (neutral/warm white) over 2700K (which can appear yellow). Since Corten steel has a natural bronze-brown tone, 3000K harmonizes perfectly and provides a more vibrant color rendering.
  • Brightness (Lumen): Outdoors in the dark, spotlighting creates stark contrasts. Do not use lumens that are too high – our LED strips at 460 lumens (5 watts) are an excellent benchmark to avoid glaring light.
  • IP rating: Adapt the lighting to the environment. An IP44 rating prevents water from reaching electrical parts (but is not fully waterproof), while IP68 is required for prolonged submersion in water.
KEYWORD

Unique & minimalistic

~ Own design

Durability

~ Durable materials for indoor & outdoor use

Carefully developed

~ Factory & designers work as a team
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