With patina or a weathered look as a new style for outdoor projects, we’ve received a lot of requests for corten steel projects such as planter boxes and edging. But did you know that not all weathered steel is corten steel?  Read on to learn the difference between weathered steel or corten and carbon steel and determine which one is right for you.

Weathered or Corten Steel

Weathering steel is a family of low carbon alloy steels consisting of a variety of grades. COR-TEN A or COR-TEN B are considered proprietary grades. The term COR-TEN® is trademarked and owned by U.S. Steel. 

COR-TEN® forms a coating of dark brown oxidation over the metal, which inhibits deeper penetration and eliminates painting needs and costly rust-prevention maintenance. With the protective rust that provides corrosion resistance, Corten steel can last upwards of a few decades to over 100 years.

Carbon Steel

This is iron with less than 1% carbon up to 2.5% carbon. If it has less than 10.5% Chromium, then it is considered Carbon Steel. Carbon steel is sometimes referred to as a ‘low-alloy’ because of its very low alloy composition.

Carbon Steel is susceptible to rust due to the absence of corrosion resistant chemicals such as Chromium. Because of this, it’s less expensive. 

Weathering steel can outlast carbon steel in outdoor conditions, so it is used for exposed steel structures frequently because it removes the need for repainting and recoating of the steel. The protective rust coating formed by weathering steel naturally, slows the corrosion rate enough to exceed its design life for other reasons.

The Disadvantages of Corten Steel

Corten Steel is significantly more expensive than other metals with a similar finish. For smaller projects, this may not be a big deal, but for larger construction sites and infrastructure projects, the difference in price can be significant. 

Over time, Corten Steel will naturally develop a rust-like appearance. While this looks great on steel, it’s not a great look on walls and pathways. The other downfall is that Corten Steel has staining issues where the rust can stain nearby surfaces, and potentially ruin walls and floors. 

Lastly, Corten Steel is not overly environmentally friendly because the run-off is not great for the environment. For those of you that have had neighbors with Corten Steel outdoor products know that runoff ends up in nearby drains and ponds, which can ultimately cause significant damage to the local ecosystem.

Which One is Right For You

To decide whether Corten Steel or Carbon Steel is right for you, consider your budget. From there decide if you’re willing to pay more for Corten Steel, which will last longer than Carbon Steel. For the inexperienced eye, Corten Steel and Carbon Steel are very similar, so mostly experts will know exactly what to look for to differentiate one from the other.  The project pictured above is made of Carbon Steel, can you tell the difference?

We are a Dallas custom metal fabrication company specializing in design, manufacturing and installation of different metal products for commercial and residential clients. Check out our portfolio of work and contact us when you’re ready to get started on your custom metal project.

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