Corten Steel: Is It Safe For Gardens?

Corten metal has more and more been employed as a viable materials for residence gardening and industrial landscaping in recent times. As a result of it’s a form of weathering metal, it has a protecting layer of corrosion-resistant patina that provides it versatility together with fascinating aesthetic qualities. 

Naturally, individuals have issues about corten metal and weathering metal typically. Whereas these issues aren’t unfounded until there may be related atmospheric corrosion – which we’ll get to later on this piece – the mechanical properties of COR-TEN metal alloys make beds manufactured from this materials wonderful for rising vegetation in most climate. 

On this piece, we’ll focus on this very subject. We’ll contact on what corten metal is, and contact on the subjects of rust and corroding. Then we’ll discuss corten metal planters and the very best practices related to them. So when you’re questioning if corten metal is best for you, learn via this piece!

What’s Corten Metal?

Corten metal is utilized in structure, however is it garden-safe? Supply: PROTEUS

Corten metal is a kind of chromium-copper alloy weathering metal that depends on a moist/dry cycle to construct up a protecting layer of rust. Because the floor develops it modifications coloration over time, starting with a red-orange hue, and ending with a purplish patina. Whereas most individuals have a unfavourable affiliation with rust, on this case, it’s what is required to develop the precise look and seal, creating a layer defending the remainder of the fabric from corroding over time. In truth, corten metal is very proof against corrosion and is utilized in notable architectural initiatives just like the Broadcasting Tower in Leeds, United Kingdom. 

Corten ASTM Designation

The unique COR-TEN A obtained the usual designation for low-alloy, high-strength, and excessive corrosion resistance from the American Society for Testing and Supplies. Newer ASTM grades for corten B metal have the identical properties however have obtained customary designations that point out it may be manufactured and utilized in a skinny sheet. The metals that compose corten metal are copper, chromium, manganese, and nickel. 

Distinction Between Corten and Redcor

An affiliation that deserves some clarification is the distinction between corten metal and redcor. COR-TEN refers to a hot-rolled metal alloy that’s used within the railroad and transport industries. Redcor is a kind of corten metal however is cold-rolled as an alternative of hot-rolled. This chilly roll helps stabilize the chemical composition because the sheet varieties, preserving it extra uniform from product to product. 

Distinction Between Corten A and Corten B

Let’s additionally focus on the variations between corten A metal and corten B metal. They’re principally the identical materials, however Corten A or the unique COR-TEN obtained the addition of phosphorus, making it extra helpful for constructing facades and gasoline flues. Corten B is weathered metal that doesn’t have this addition and is best for giant constructions. There are different slight variations between the chemical compositions of the 2 sorts of weathering metal, however one necessary factor to notice is Corten A will not be used within the growth of Birdies corten metal planters. 

An attention-grabbing a part of the event of those planters is that they’re utterly secure for rising meals. The quantity of iron-oxide launched into the soil through the rust course of is non-toxic and won’t disadvantageously have an effect on vegetation.

The Rust Course of

Runoff stains on concrete from corten A
Corten could trigger staining on concrete as seen on this picture. Supply: nicolas.boullosa

Let’s look at the subject of rust in corten metal extra intently. The protecting layer of rust that develops on weathering steels is secure for vegetation, not solely as a result of the quantity of iron, manganese, copper, and nickel are non-toxic, but additionally as a result of these micronutrients are necessary for rising wholesome vegetation. The protecting patina that develops on the metal is beneficial on this means. 

However there are architectural research that recommend corten A metal might be an environmental contaminant in giant quantities, in situations that velocity the corrosion course of. Be aware these research usually are not related to corten B metal or Redcor, and Birdies beds are manufactured from Redcor. One other factor to notice about this research is that it occurred on the facade of a big constructing over a number of years of publicity. So giant quantities of corten A could have a chemical composition that’s detrimental to the surroundings. However in smaller quantities, corten metal materials in the precise environmental situations is non-toxic.  

Because the rust layer develops, the tensile energy of the COR-TEN B weathered metal turns into stronger and extra corrosion resistant. Those that stay in situations the place atmospheric corrosion is extra possible (resulting from environmental situations) can enable the corten metal to succeed in the rust coloration they need, then apply sealing supplies to assist the construction keep not solely the precise coloration however integrity as nicely.  


The principle concern most individuals have about corten steels is their sturdiness. In a raised mattress type in the precise surroundings, COR-TEN steels are proof against corrosion. For this reason this metal was chosen for constructions in constructing and structure (within the Broadcasting Tower in the UK, as an illustration) earlier than it was employed in gardening initiatives. 

Nonetheless, this resistance is essentially depending on the climate and local weather in an space. The right oxidation happens in optimum moist/dry cycles. Areas that have excessive humidity expertise a number of challenges relating to the power of COR-TEN metal to stay sturdy. Moreover, resistance to corrosion is decrease in areas with salt spray – particularly in coastal areas. Folks residing on the seashore expertise larger corrosion charges with their cor ten metallic beds.

That’s why these residing in these atmospheric situations ought to go for Aluzinc coated galvanized metal beds as an alternative, just like the Birdies Unique 6-in-1 metallic raised mattress. Fortunately, galvanized metal is secure for gardens, too!

Nonetheless, corten metal beds uncovered to fog, snow, rain, or different moisture are protected by the rust fashioned on the floor of the alloys that make up this weathering metal. And so they have the additional advantage of a particular type that comes from the hue of the protecting coating. 

How Lengthy Does Corten Metal Final?

So long as the beds manufactured from corten metal aren’t subjected to the extreme atmospheric corrosion we’ve mentioned up up to now, they’ll final for years. The rust that develops on them creates a layer that gives corrosion resistance and better tensile energy. That’s why cor ten is used worldwide in landscaping and even household residence gardening. 

The metal’s rust layer builds up elevated resistance to degradation, which is why it has been the premiere weathering metal materials utilized in development and structure for years.  

Corten Metal Raised Beds

Urban Tall 9-in-1 Bed
The City Tall 9-in-1 Mattress reduces again pressure whereas nonetheless trying nice.

Whereas we’ve touched on the final type of corten metal up up to now, and we’ve talked about its use in constructing and different architectural initiatives, let’s focus on the very best practices for rising vegetation in corten metal raised beds. Once more, in most environments, the atmospheric corrosion resistance that happens on corten metal raised beds truly makes them extra corrosion resistant than different supplies. However utilizing COR-TEN and understanding the method of patina formation will enable you to decide the very best placements and makes use of for you. 


Outdoors of enormous constructing development and structure, there are tons of corten metal makes use of. Probably the greatest developments within the frequent manufacturing of weathering metal is the creation of trendy and putting backyard beds. The shape through which these corten metal beds come is manifold, with choices for shoppers that embrace conventional raised beds (just like the Birdies City Brief 9-in-1), and even small planters that may sit on prime of a railing or counter. There are even spherical planters which can be wonderful for any city gardener. 

As they rust, the yield energy of the metal alloy regenerates repeatedly, bettering the look and the corrosion resistance of the mattress’s exterior as it’s uncovered to the weather.  


As a result of the alloys rust and the floor supplies within the development of corten metal beds do runoff, it’s finest to position them on the earth, or in an space the place this runoff isn’t an issue. In enterprise complexes the place planters could also be positioned on the pavement, the weathering metal floor will leach onto surfaces, particularly after wet climate. Whereas this isn’t a structural downside as a result of the alloy regenerates repeatedly because the metallic rusts, any floor that the beds are on will accumulate that run-off materials. If you wish to know find out how to clear any creating stains, try the final part of this piece. 

This isn’t a menace to the surroundings, neither is it a menace to the vegetation you’re rising as we’ve talked about. The yield energy of the metallic will maintain up on the identical charge as it could when positioned immediately on the earth. It’s extra of an aesthetic concern as a result of the metallic can stain concrete with out steady monitoring and upkeep. Weathering metal that runs off onto a floor must be instantly cleaned up via steady cleansing or energy washing of the floor it’s on. In any other case, you may place your corten metal beds on rust-colored gravel, cardboard, or just grime to stop staining. 

Accelerating Corrosion

One other attention-grabbing subject concerned in corten metal beds is the power for shoppers to speed up the corrosion to their desired type on their very own. The beds are shipped straight from the manufacturing unit and coated to stop corrosion earlier than they arrive. As soon as that layer is uncovered to climate patterns, it wears off, and the pure strategy of rusting takes place on the metallic floor. However at residence, you may make the weathering metal rust synthetically to your required coloration.

To hurry rust your corten metal mattress, mix 2 ounces of vinegar, ½ teaspoon of salt, and 16 ounces of hydrogen peroxide in a sprig bottle. Shake the bottle vigorously to mix the elements. Put on gloves and goggles. Spray your complete metallic planter field. Wipe it with a towel if the feel on the planter wants smoothing. This speeds the event of the patina, and a protecting coating varieties on the oxidized metallic. Repeat the method over time, permitting it to dry between remedies till you obtain the specified look in your metallic planter. 

The method of accelerating corrosion in your corten metal mattress is straightforward and might happen over a number of functions of the selfmade answer. That is yet one more advantage of working with corten metal within the backyard. 


When you’ve oxidized the corten metal, or as soon as it’s reached your required oxidation naturally, you may seal the metallic to stop additional rusting. There are various sealants available on the market which can be acceptable for a venture of this sort. Polyurethane-based sealants are finest. Be aware that the seal will darken the mattress’s exterior. That’s why it’s finest to check earlier than you decide on a seal. To do that, choose a small space of the mattress and apply the sealant. Permit it to dry utterly. Then examine the colour to see if it matches your required look. When you’re glad with the completed look, apply the sealant over your complete exterior of the mattress. 

Cleansing Corten Stains

Let’s say that you just’ve already positioned your mattress on a concrete floor and you’ve got stains creating. Not an issue in any respect! Chances are you’ll need to take a look at this cleansing answer on a small space of the pavement to make sure it creates your required end result. Find a bottle of vinegar or discover some lemon juice. Pour both (or a mix of each) on the stain and permit it to take a seat for a number of minutes. Then, scrub the realm with a wire brush, and rinse away the cleaner. Reapply the answer and repeat the method as wanted to take away the stain.

The Inexperienced Thumbs Behind This Article:

Leave a Reply

GIPHY App Key not set. Please check settings