Corten woven steel panels

What is Corten steel?

And
is it a better choice for edging and fencing?

We offer both mild steel and Corten steel edging and fencing.

What is Corten steel is one of our most frequently asked questions, after, how quickly can you deliver?

In this short article, we look at Corten steel and compare it to mild steel used for fencing or edging.

Our Mild steel fencing
Our Mild steel fencing

What other names is Corten steel known as?

You may have seen Corten written as COR-TEN, Cor-ten or even Cor-10. Either way, the Cor refers to Corrosion resistance and the Ten is tensile strength.
It is also commonly known as weathering steel due to its resistance to corrosion once it has weathered.

COR-TEN is a brand name for a steel developed by U.S steel back in the 1930s. However, their metal plate business was sold to the International steel group but, U.S steel kept the rights to the name so, if you wanted to split hairs COR-TEN or Corten etc is not actually available! Instead, the standard designation A242 (COR-TEN A) and A588 (COR-TEN B) are now sold.

So what in Corten steel?

In essence, it is a small number of steel alloys created in 1910 which were designed to be stronger and more resistant to weathering. This is in part achieved by increasing the amount of phosphorus and copper.
Developed initially to construct railway carriage hoppers, it was soon discovered that once the steel surface had corroded it stabilised and formed a protective layer to the metal below.

The practicality of Corten soon led to it being used for other areas of construction to include bridges, cranes and shipping containers, for which it is still used today. While being practical, many prominent artists and architects also fell in love with the rusted patina of Corten producing stunning constructions around the globe clad in Corten. These include the John Deere HQ in the USA, The Angel of the North, The Barclays sports arena in New York and Leeds Broadcasting tower.

Leeds broadcasting centre
Leeds broadcasting centre

How has it become so popular in gardens?

The use of Corten steel in high profile constructions by equally high profile designers has put it in the public domain and propelled its popularity in recent years. Corten has now become almost a household brand name being available in everyday items such as fire pits, water features and of course edging and fencing.

Whilst the initial excitement of Corten in the use of architectural masterpieces has tapered, due to the fact rusted steel has been around for a millennia, it’s a very practical option and (in our opinion) blends beautifully in a garden setting it is hard to see the tide turning on its popularity or it ever going out of fashion.

Difference of appearance between mild and Corten steel

In short, the untrained eye and most likely the trained eye would struggle to tell the difference after a year outside in the UK. Corten tends to be slightly more orange than mild steel due to the copper content.
Environmental factors such as humidity and salt in the air tend to have larger effects on the appearance of both types of steel than the difference between them. The appearance can even vary in the same garden, the difference between steel in a shady corner or a dry sunny spot for example.

Corten will weather initially at a faster rate, typically a couple of months outside, whereas mild steel will take up to a year to develop the same brown patina. Rust accelerants can be applied to both bringing the process down to a few days, in our opinion be sparing though, as they are quite aggressive.

Can you tell if it’s Mild or Corten edging? (It’s mild steel)
Can you tell if it’s Mild or Corten edging? (It’s mild steel)

Advantages and disadvantages of Corten steel vs mild steel

– The main advantage of Corten is its lifespan.
It’s hard to quantify as environmental factors have a large bearing. As a guide mild steel can degrade at approximately 10 microns a year (0.01mm), so that’s 10 years for just 1mm thickness (which is why we are happy to guarantee our edging for 25 years!)
Corten will even surpass this at approximately 40 years per mm.

– Corten has more tensile strength, not especially noticeable when used for fencing and edging but comes into play when used for construction.

– Corten is much less likely to rust stain your patio. If setting edging or fencing on top of paving we advise using Corten but allow it to rust prior to installation, any staining is then very minimal compared to mild steel. Please get in touch for more information on ways to avoid rust staining altogether.

–  The main disadvantage of Corten steel is the cost. While it is a more expensive material compared to mild steel, it is only produced in sheet form so requires cutting into strips before it can be used to make edging or fencing, this adds to the cost.

–  Due to the added production to cut the Corten into strips, lead times for delivery are around 1 week longer than mild steel in our products.

– The weld points in Corten can weather at different rates, it’s not a big deal with regards to Corten edging or fencing as these are minimal and usually on the unseen face.

Is Mild steel or Corten steel the best choice for edging and fencing?

This is probably more of an opinion as the choice is largely a personal one, but knowing what we know here is our take on it…

Edging

Yes, Corten will outlast mild steel and has more tensile strength, but when a 6mm thick mild steel edge will be looking good for at the very least 25 years and have practically the same appearance we don’t feel that in most cases the advantages of Corten edging are worthy of the extra cost.

Cases where we feel Corten is worth the extra expense is generally where rust staining may occur. Bear in mind that water carries the dissolved steel so if you set your edging on top of a light coloured porcelain patio for example then mild steel will produce rust stains and continue to do so. If you allow the Corten to rust first, then install it, then any staining would be very minimal if at all. For your peace of mind though rust staining from mild steel is not an issue on gravel, borders and lawns, etc.

If you have Corten steel in your garden already and you’re looking for a fence or edge to match exactly, then it’s probably a good idea to go for Corten too, bear in mind though that different conditions will affect the colour of the steel. We have found that edging in the ground tends to weather darker than steel in dry conditions.

Fencing

Like the edging mild steel will outlast any timber products many times over, so longevity may not make Corten worth the extra cost.

Our self build woven steel fencing is offered in mild steel although, we can price for Corten weaving slats, bear in mind the round tubes (posts) are still mild steel as Corten is only produced in sheets.

Our self fit fencing panels are in fact made from Corten steel. This is due to the way they are made, Corten steel sheets are cut into slits. If we made them from mild steel production would be the same. As in this case, there is no additional production cost for using Corten, just the extra materials cost we feel this is a good option for those who are keen to use Corten without paying too much more than mild steel.

What is Corten steel?
Our woven steel Corten fencing

Do our customers buy more Corten or mild steel products?

You may be surprised to know..

For us, mild steel is the most popular, with the edging we supply at least 10 x’s more mild steel than Corten and at least 7 x’s more fencing meterage in mild steel than Corten.

The last word from us

It’s probably not helpful to get too caught up in the Corten brand, but if you are looking for the actual advantages that Corten brings and feel it is worth the extra cost then it’s right for you.

Otherwise you’re already taking big steps in terms of achieving the best in aesthetics and longevity in sourcing your steel edging and fencing from us. So take comfort in the advantages that mild steel will bring you over other materials on offer.

That said…
Whether you’re looking for Mild steel, Corten, galvanised and even stainless steel edging or fencing, we are all ears and will do our best to provide exactly what you’re looking for!

Share Post: