What is Corten Steel?

March 22, 2018

You’ve may have heard us talk about how Tuff Box containers are created from 14-gauge Cor-Ten Steel, but you may want to know more about it, and why it’s so important that we mention it when discussing our containers. This article will talk about steel grades, the differences between them and why corten steel is such a great material to use for our storage containers.

Grades of Steel

There are thousands of ways to chemically create steel products. Alloys can be mixed and added to iron in order to give the final material certain benefits or different strengths (called properties). With each variation, we have completely different steel, so there have been advances in order to help us “file” or organize them and give them individual names that will make the stand apart from each other. Once such popularly used system is the unified numbering system (UNS). This system is an alloy designation widely accepted around North America and it is managed by both the ASTM International, an international standards organization that creates and publishes multiple voluntary consensus technical standards, and SAE International, a United States-based, professional association and standards developing organization.

Using this standardized system for identification, we can now figure out what properties each steel will have, and thus we have our “grades” of steel.

Corten Steel and Others

As we mentioned, there are multiple types of steel out there in the world, and many of them have plenty of the same benefits, however they don’t all stand up the same, or can be used in the same ways, with the same results. So in this article, there are two main types of steel that we will be focused on; Mild Steel and Weathering Steel.

Carbon or “Mild” Steel

This steel type can also be called “low carbon steel”, because it does not contain a lot of carbon. It also does not contain a large amount of alloys. Chemically, there is quite a bit of difference between a typical carbon steel and corten. Mild steel is primarily made of iron, with very little carbon and few alloys added. This means it can be much more easily welded, machined, and it is nearly impossible to strengthen through heating and quenching. It is a popular choice for many applications that require strength and durability, but may not require the protection against the harsh elements.

Corten or “Weathering” Steel

Corten is a copper chromium alloy steel, meaning it has other materials besides iron in it. Because of this particular chemical composition, there is an early formation of oxidation (rust) that acts as a protective layer against harsh elements and weather and this is why it is so special. Normally, rust is a bad thing, and something we try to avoid. However, this specific type of oxidation (or rust) prevents worse degradation to the steel and lengthens the life of the steel overall. Because of this, corten steel can withstand the worst of the seas and weather across the world and keep doing its job and that’s why it is frequently used in bridges and towers, in chimneys and for rail cars; things that may be outside for long periods of time and need to withstand harsh weather.

More About Corten and Weathering

You will see corten steel sometimes written as “COR-TEN” and it is also commonly referred to as “weathering steel”. Corten is actually the trademarked name of this steel type and when it is exposed to the elements, its chemical makeup creates an early petina of light rust that sticks to the surface of the steel and actually adds the layer of protection we talked about. The Corten steel brand name covers a few steel types or grades of steel such as ASTM A588 and A242.

While on the ocean, containers must resist pounding salt water, wind and rain. They have to stay in the glare of the direct sun, day in and day out. A typical, carbon steel, or mild steel, can take a little of the same abuse, but for less amount of time because of the pace they degrade and rust through. Corten’s particular oxidation slows down the process and helps to protect itself from the harsher elements. Eventually, however, they will also break down like their mild steel type cousins. Typically, corten steel lasts 2-5 years longer in the harsher environments, making it perfect for shipping containers. And the lifetime of these containers can last even longer when used in primarily less hazardous conditions, such as in the Midwestern United States.