Most low alloy steels have the tendency to rust, or corrode, over time as they are exposed to water and/or moisture in the air. Overtime, this rust layer becomes porous and detaches from the metal surface. One of the benefits of using corten steel, also referred to as weathering steel, is its ability to resist the corrosion that other low alloy steels experience.
Is corten steel rust proof?
With corten steels, the rusting process occurs in a similar fashion, but instead produces a stable rust layer known as the patina, which adheres to the base metal and is much less porous. This naturally-developed patina regenerates continuously when exposed to weather and produces a protective barrier that impedes further access of oxygen, moisture and pollutants.
So, does this make corten steel rust proof? No, it does not. Corten steel is allowed to rust in order to form the protective patina coating. While this results in a much lower corrosion rate compared to other steels, it does NOT mean corten steel is rust proof.
Patina vs. rust
Patina and rust both are forms of surface corrosion.The patina forms through oxidation and protects corten steel from the deeper and more destructive rust. Rust, on the other hand, is caused by deterioration, and will begin to chip away the metal surface creating porous cracks and hazardous edges.
In its original state, corten steel is silver in color like standard steel and develops the orange-brown color overtime as the patina develops. 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 environmental cycles. Likewise, cold-rolled materials (18 GA sheets or thinner) form the patina quicker than hot-rolled materials (16 GA sheets or thicker).
Many will mistake the orange-brown patina that corten steel produces as rust, but in reality, the patina of corten steel is doing its job to guard against further corrosion. That's the beauty and benefit of using corten steel!
Company profile
Founded in 2008, Gnee (Tianjin) Supply Chain Group Co., Ltd. specializes in the global trade and processing of Corten steel products.
• We handle all kinds of Corten engineering projects, such as bridges, gardens, hotels, and facade systems.
• Compliant with ASTM, EN, and other international standards; third-party inspection supported.
• Exported to over 200 countries and regions worldwide.
• 8 subsidiaries across China and overseas, ensuring global service coverage.
Application Fields: Architecture, landscaping, gardening, cladding, and urban infrastructure.
