Corten Steel Explained: Why It Suits British Gardens

If you have looked at fire pits or outdoor kitchens recently you will have seen corten steel: that deep orange-brown, visibly rusted finish that somehow looks deliberate rather than neglected.

It is deliberate. Here is how it works and why it suits the British climate particularly well.

What corten steel actually is

Corten, more properly called weathering steel, is a steel alloy containing small amounts of copper, chromium, nickel and phosphorus. Those additions change how the steel corrodes.

Ordinary steel rusts in a way that flakes off, exposing fresh metal underneath, which then rusts in turn. The process continues until there is nothing left. Weathering steel rusts differently. It forms a dense, tightly-adhered oxide layer that seals the surface and dramatically slows further corrosion.

In other words, the rust becomes the protective coating. No paint, no galvanising, no annual treatment.

Why it works well in the UK

Weathering steel develops its protective layer through repeated wet and dry cycles. British weather provides those in abundance. A corten piece here typically develops a stable patina within six to eighteen months.

It also means no maintenance in any meaningful sense. You are not sanding, priming or repainting. The finish looks better as it matures rather than worse.

You will find corten across our range in Adezz Forno flue components such as stovepipes and raincaps, in Barbecook's Nestor and Pedro barbecues, and in fire pit designs.

How the patina develops

• Weeks 1 to 4. A bright, uneven orange appears. This stage looks patchy and alarms people. It is normal.
• Months 2 to 6. Colour deepens and evens out into a richer russet.
• Months 6 to 18. The patina stabilises into a dark brown-orange and largely stops changing.

Rain patterns, shelter and orientation all affect how evenly it develops. A piece under a tree will weather differently to one in open ground.

The one thing to plan for

During the first several months, rain running off corten carries iron oxide with it. That run-off stains, and it stains permanently on porous surfaces.

Light paving, limestone, sandstone, decking and painted walls are all at risk. Plan for this before installation rather than after:

• Site corten on gravel, dark paving or grass where staining will not show.
• Use a drip tray or gravel bed beneath during the first year, when run-off is heaviest.
• Keep it clear of light-coloured render and rendered walls.

After the patina stabilises, run-off reduces substantially, but it never stops entirely.

Corten versus stainless steel

These solve different problems. Stainless resists corrosion by staying bright and needs cleaning to stay that way, particularly near the coast where salt attacks lower grades. Corten embraces corrosion and needs nothing, but stains what is beneath it and continues changing appearance.

For food-contact surfaces, grills and worktops, stainless is the right answer. For structure, cladding, flues and fire bowls, corten is often the better long-term choice.

Our guide to protecting outdoor equipment through winter covers how each material should be treated seasonally, and the outdoor kitchen buyer's guide goes further on material selection.