What Is Corten Steel? 

Corten, or weathering steel, is a low-alloy steel material that creates its own protective coating when exposed to the elements.  

Instead of being painted or sealed, it naturally oxidizes, forming a thin layer of rust that protects the metal underneath from further corrosion. 

The surface is alive — it changes over time as it reacts to the environment. Rather than being a flaw, this evolution is exactly what makes Corten steel so durable and distinctive.  

How the Patina Forms 

Corten steel starts out as a dark blue-grey color. When it's exposed to the elements, and moisture and oxygen interact with the surface, it starts to develop an orange-brown hue.  

Over the course of several months to a few years, the color will deepen — eventually turning a rich brown, and in some climates, nearly black.  

This gradual transformation is what gives Corten steel its warm, organic look. 

What to Expect During the Aging Process 

In the early stages, the surface of your Corten steel product may appear uneven. You might notice streaking, splotches, or light and dark patches. 

This is completely normal. These variations are simply areas that have experienced different wet/dry cycles — over time, the color will even out as the patina develops. 

If your product arrives looking slightly different than a photo online, it’s because it’s in a different stage of its natural weathering cycle. Every piece is truly unique. 

Why Each Piece Looks Different 

The final appearance of Corten steel depends heavily on local environmental conditions, including: 

• Humidity and rainfall — more moisture accelerates patina formation 
• Sun exposure — UV and heat influence tone and texture 
• Air quality and pollution — urban vs. rural settings create subtle differences 

Because of these natural factors, two identical products can look different within just a few weeks of installation — and that’s part of the charm. 

Rust Runoff & Surface Protection 

As Corten steel forms its patina, you may notice some rust runoff or “bleeding” during the first few months. This is normal and temporary. 

However, rust runoff can stain light-colored surfaces like concrete, stone, or stucco. To prevent this, we recommend placing your Corten steel product on a non-porous surface. You can also let it weather outdoors for a while before final placement.  

Self-Healing Surface 

One of the best qualities of Corten steel is its ability to self-heal. If the surface is scratched or scuffed, it will simply rust again to match the rest of the finish.  

This makes Corten Steel products incredibly low-maintenance and ideal for outdoor environments.