There are several uses and types of steel when it comes to modern applications, and one broad area that’s important for many of these is corrosion resistance. Many forms of steel will be placed in environments where rust and other forms of corrosion are possible – this would be a problem for certain kinds of steel that don’t have the proper protective alloys, but for others with the right qualities, there won’t be an issue.

At Wasatch Steel, we’re happy to offer a huge variety of steel products and services, from steel sheet and bar to steel workshop tools, abrasives and many others. One of the steel materials that’s often used in applications where corrosion is a risk, such as for architectural or landscaping needs, is known as Corten steel – what is Corten steel, what other terms is it sometimes referred to by, and why is it beneficial for certain specific applications? Here’s a primer.

Basics on Corten Steel

Corten steel will often be referred to by the more general term “weathering steel,” but technically speaking, they’re not identical. Corten steel, rather, is actually a short-form for COR-TEN, a branded and trademarked form of steel. The “COR” refers to corrosion resistance, which we’ll get to in a moment, while the TEN reflects the excellent tensile strength typically offered by this form of steel.

Now, this doesn’t mean you have to correct someone in the industry who uses these two terms interchangeably – this is common and expected in many circles. Certain clients may require the specific COR-TEN proprietary product, but in most cases, weathering steel – which has nearly identical properties – will be acceptable as well.

ASTM Designations

Within the ASTM, formerly known as the American Society for Testing and Materials, there are a few different designations for Corten, or weathering, steel. These include (but are not necessarily limited to) each of the following:

• ASTM A588: Generally used in steel bar format for various different structural applications, including those that require different shapes.
• ASTM A606-4: A specific type used for cold-rolled or hot-rolled steel sheet or steel coil.
• ASTM A242: Used only for steel plate applications.
• ASTM A709-50W: Able to be utilized in both steel bar and steel plate formats, this type is often found in bridges and similar structures.
• ASTM A847: This product is perfect for steel tubing and pipe, and is the most common option for these materials.

General Benefits

In many cases, Corten or weathering steel will be used less for practical reasons and more for aesthetic ones. It has a distinctive appearance that makes it ideal for many forms of architecture, sculptures, landscaping work and similar uses, and these are some of the most common areas where you’ll see it.

However, Corten steel does have some definite benefits from a practical standpoint. It requires very little maintenance compared to other metal types, for instance, and is low-cost – plus lasts many years, making its cost-efficiency quite high. It’s also durable, plus has strong corrosion resistance properties that allow it to be used for major public structures such as bridges. However, as we’ll go over in our next section, it’s important to know the specifics of its corrosion resistance before utilizing it.

Rust Considerations

Specifically, it’s important to separate the terms “corrosion resistance” and “rustproof” in this situation. Corten and weathering steel generally qualify easily for the former term, but do not for the latter – and this is important when considering its uses and applications.

In particular, it’s important to consider the level of protection involved. Corten steel is resistant to corrosion based on the common presence of a patina, or rust, which may show some visible signs but will also protect the metal from much more harmful forms of corrosion and atmospheric interference. But how long this patina will last is the crux point to consider for its application, and the answer here depends on a few environmental and climate-related factors. Here are some general tips on Corten steel, rust and corrosion resistance:

• In most cases, Corten steel will begin to show its patina within six months or fewer of exposure to atmospheric risks. This timing is due to a need for multiple wet/dry cycles to take place on the metal, allowing it to oxidize over time.
• However, for applications where the steel needs to rust even faster than this, there are methods for allowing this to happen. Either saltwater alone, or an application of saltwater mixed with vinegar and peroxide, is known to speed up the rusting process in Corten steel, allowing it to provide corrosion protection almost instantly.
• If this rusting process is done correctly during application, it’s possible for Corten steel to last – and provide this corrosion protection – for an incredibly long period. Its average lifespan is over 20 years, with many applications of Corten or weathering steel lasting over a century without any issues.

Common Applications

For the above reasons, and as we’ve touched on in a couple spots here, there are several modern applications of Corten or weathering steel. It’s often found in bridges, for one, where its corrosion resistance and durability combination is excellent. You will also see it on numerous outdoor sculptures and various landscaping settings. It’s also commonly utilized in various marine applications, where corrosion resistance is at a premium, or even on roofing and signs – materials that will be exposed to plenty of rain and moisture.

For more on the common uses and qualities of Corten, or weathering, steel, or to learn about any of our steel products or services, speak to the staff at Wasatch Steel today.