Corten steel is a type of weathering steel, made from iron with small amounts of alloying elements including copper, chromium, nickel and phosphorus. These additions change the way the steel responds when it is exposed to air and moisture.
Left outdoors, the surface begins to oxidise and develops the familiar orange, russet and deep brown patina associated with Corten. Over time, that outer layer becomes more stable and helps slow the rate of further corrosion.
The result is a material with a very particular combination of strength, durability and warmth.
It is easy to see why it has found a place in garden and landscape design.
Corten works with the changing colour of a garden across the seasons. In spring and summer, its warm surface creates contrast against fresh green planting. By late summer and autumn, it begins to sit among seed heads, grasses, timber, bark and changing foliage. Through winter, it holds colour when much of the garden has receded.
It also suits the way outdoor spaces age.
Rain, temperature and exposure continue to influence the surface, so the material develops gradually in its surroundings. The patina can vary from one location to another, giving each piece its own tonal variation and character.
That ability to weather in place is a large part of Corten's appeal. It can sit comfortably alongside stone, concrete, timber and planting, and it works equally well in highly architectural spaces and looser, more natural gardens.
Today we see it used for planters, retaining walls, garden edging, sculpture, water features and outdoor fires. Its influence has travelled further still, helping make rust and oxidation part of the wider visual language of contemporary garden design.
But Corten began somewhere very different.
From industry to architecture
Weathering steel was developed in the United States in the 1930s for demanding industrial applications. The name COR-TEN was derived from two of the qualities the material was designed to provide: corrosion resistance and tensile strength.
Its practical properties eventually attracted architects and designers, who began to see possibilities in the surface itself.
Rather than treating weathering as something that had to be hidden, they allowed the material to change visibly.
One of the important early architectural examples was Eero Saarinen's Deere & Company headquarters in Illinois, completed in the 1960s. Weathering steel was used extensively across the building, bringing an earthy, textured quality to an otherwise modern architectural structure.
From there, Corten became increasingly associated with architecture, landscape and sculpture.
And with that came a wider shift in how rust itself was perceived.