Watch the Patina Develop on Central Steel’s Warehouse

How the patina develops on weathering steel

Watch the Patina Develop on Central Steel’s Warehouse

Weathering steel, also referred to as COR-TEN steel, is designed to provide enhanced mechanical properties and resistance to atmospheric corrosion. Weathering steel naturally develops a protective patina layer, which regenerates continuously as it is subjected to weather to guard against corrosion. 

While the patina provides sought-after practical protection, it also produces an aesthetically-pleasing look that many of our customers and end-users seek when they select weathering steel. The patina gives the steel a rustic texture and yields an orange-brown color depending on the age of the patina.

From modern construction to natural areas, this color and texture blends well with just about any environment. However, much to many’s dismay, weathering steel is silver in its original state, just like standard steel, and develops the orange-brown color over time as the patina forms.  

How long does it take weathering steel to patina?

As a high strength weathering steel supplier, we’re often asked how long it takes for corten steel to form the patina. The rate at which the patina forms depends on the environment the steel is in as well as various factors, such as humidity and proximity to bodies of water. 

In our experience, the patina forms quicker when the steel is exposed to more wet and  cycles. Likewise, cold-rolled materials (18 GA sheets or thinner) tend to form the patina quicker than hot-rolled materials (16 GA sheets or thicker).

Watch the patina develop on Central Steel’s Warehouse

Because the timeline of patina development is so frequently asked about, we like to show you how the patina develops through photos of different applications of weathering steel. Today, we’ll show you how the patina formed on our warehouse. 

Central Steel’s warehouse was built out of  cold-rolled 22 GA A606-4 weathering steel sheet. As you’ll see in the photos below, the patina began developing immediately after it was constructed on May 11, 2022. 

Weathering Steel Patina Development

May 25, 2022 – 2 weeks later


Weathering Steel Patina

June 8, 2022 – 4 weeks later


Weathering Steel Patina

June 20, 2022 – 6 weeks later


Weathering Steel Patina

July 14, 2022 – 10 weeks later


Weathering Steel Patina

August 14, 2022 – 14 weeks later


Weathering Steel Patina Development

September 20, 2022 – 19 weeks later


While the patina is still not fully developed in the final photo, you can see how much it darkened in color over the course of 19 weeks. 

Want to see more patina timelines? Check out these blogs: 

Get the answers to frequently asked questions: 


Contact an experienced sales representative at Central Steel Service to learn more about how the patina would develop in specific areas!