What is Corten Steel and Why Do Landscapers Love It?

If you have spent any time browsing modern garden design, you have almost certainly seen Corten steel — that warm, rust-coloured metal used for garden edging, raised beds, fire pits, and feature walls. But what exactly is it, and why has it become such a popular choice for landscapers and architects?

What is Corten Steel?

Corten (also called weathering steel) is a group of steel alloys developed in the 1930s by United States Steel. The key difference from regular mild steel is its composition — it contains copper, chromium, nickel, and phosphorus, which cause it to form a stable, tightly-adhering rust layer when exposed to the weather.

This patina layer is not ordinary surface rust. It is a dense oxide that acts as a barrier, slowing further corrosion dramatically. Once fully developed — typically after 1–3 years of weathering — Corten steel requires virtually no maintenance.

How Does the Patina Develop?

The patina goes through several stages:

• Weeks 1–4: Fresh steel turns orange-brown as initial oxidation begins.
• Months 1–6: The surface darkens and the colour deepens to a rich amber-brown.
• Year 1–3: The patina stabilises into a dark, velvety chocolate-brown texture.

The rate of development depends on your climate. In Melbourne, the alternating wet and dry conditions are ideal for a well-developed patina.

Why Landscapers Love It

• Low maintenance: No painting, sealing, or annual treatment required once the patina forms.
• Longevity: Properly installed Corten edging and features last decades.
• Aesthetic: The warm earthy tones complement native plantings, timber, and stone beautifully.
• Versatility: It can be cut, bent, welded, and formed into almost any shape.
• Sustainable: Steel is 100% recyclable at end of life.

Common Uses in Landscaping

At MetFab, we supply and fabricate Corten steel for a wide range of applications including garden edging, raised planter boxes, retaining walls, fire pits, water features, screen panels, and garden rings.

Things to Be Aware Of

During the initial weathering phase, Corten steel will weep orange stain onto adjacent surfaces — pavers, concrete, and rendered walls can be affected. Plan your installation to allow for this, or protect adjacent surfaces until the patina stabilises.

Corten is not suitable for permanently submerged applications or enclosed environments with no airflow, as it needs the wet-dry cycle to form its protective patina.