Shipping containers are usually made of Corten Steel, an alloy weathering steel, commonly used in construction and shipping industries because of its robust characteristics. It is globally recognised by its branded trademark name, COR-TEN Steel.
The History of Corten
Corten was developed by the United States Steel Corporation in the 1930s when there was a need to create steel that could withstand exposure to the elements without regular maintenance. A patent was created for a steel with good mechanical resistance and ‘controlled corrosion’. Its trademark name, COR-TEN steel, was formed using a combination of the steel’s two properties – corrosion resistance and tensile strength. Its intended use was for railway hopper cars to transport heavy bulk loads, including coal, metal ores, mineral products and grain, making it ideal for shipping container construction. Later that decade, painted Corten was used for railroad passenger cars. Corten Steel became increasingly popular in construction and architecture because it requires little to no maintenance. In recent years, it gained further popularity for aesthetic reasons as it adds a unique, weathered finish to modern statues and sculptures.
The Characteristics of Corten Steel
Corten Steel has high tensile strength and corrosion-resistant properties, which are achieved by adding specific alloys such as copper, chromium, nickel, and phosphorus to the base metal. When exposed to the elements, particularly atmospheric conditions containing oxygen, moisture, and pollutants, Corten Steel uses a chemical composition that oxidises over time to create its own protective film instead of corroding or rusting. It’s often used for its decorative finish as the oxidation gives a unique rust-colour appearance. Shipping containers made from Corten Steel are highly durable and resistant to rust, making them ideal for storing and transporting cargo by boat worldwide. The units have an additional layer of protection to prevent them from rusting: corrosion-resistant properties of Corten Steel ensure that the containers remain structurally sound even in harsh marine environments, prolonging their lifespan and reducing maintenance requirements. Units may appear rusty, but this “rust” won’t cause corrosion, thanks to their self-preserving properties.
Corten Explained
Classed as a ‘weathering steel’, Corten can resist corroding in extreme weather conditions like rain, snow, or ice. It does this by creating a dark brown oxidised coating over the metal. The oxidised layer protects the unit and prevents any outdoor elements from penetrating the metal further, which in turn prevents corrosion. The oxidised coating not only prevents corrosion damage but also needs very little maintenance in the long term. The oxidised appearance means that painting your unit is optional. If it does need to be painted to blend into landscaping, it can easily be powder-coated in any RAL colour.
What Are The Advantages of Using Corten Steel?
- Corrosion Resistance: Corten Steel forms a protective layer of rust, preventing further corrosion and extending the lifespan of shipping containers.
- Durability: Corten Steel containers are highly durable and capable of withstanding harsh weather conditions and rough handling during transportation.
- Low Maintenance: The natural patina formed on Corten Steel eliminates the need for regular maintenance, such as painting, reducing maintenance costs over time.
- Aesthetic appeal: The unique appearance of Corten Steel, with its rusted surface, adds aesthetic value to shipping containers and enhances their visual appeal.
Are There Any Disadvantages of Using Corten Steel?
Staining: During the initial weathering process, Corten Steel may cause staining on surrounding surfaces due to runoff of rust-containing water. Staining can occur on both regular carbon steel and Corten Steel.
How to Minimise Staining on Corten Steel:
Surface Treatment: Applying a protective coating or sealant can help minimise runoff and staining during the initial weathering phase. Proper Drainage: Ensuring adequate drainage around Corten Steel structures can help prevent stagnant water from accumulating and causing excessive runoff. Maintenance: Regular cleaning and maintenance can help manage staining by removing accumulated rust and preventing runoff onto adjacent surfaces. Strategic placement: Consider the location and orientation of Corten steel structures to minimise runoff onto sensitive surfaces.
How Is Corten Steel Made?
Corten is made by melting additional elements, such as copper, nickel and chromium, and adding them to the steel during the production process. The product is then passed between high-temperature rollers, which move any iron waste material to the surface. The process can be used to create Corten A (Type 1) and Corten B (Type 2). The type created is dependent on the amount of phosphorus melted into the product, which alters the properties of the final product: Corten A is up to 12mm and is often used in sheets or coils. It has a higher level of phosphorus and copper, which helps produce the oxidised finish. Corten B is thicker, ranging from 15mm to 50mm, and is produced in plate form.
Most Common Uses of Corten Steel
Due to its strength and resistance to weather damage, there are several uses that Corten lends itself well to. It is ideally suited for shipping containers, as it ensures the container has longevity. As the oxidised layer forms, it protects the steel box and prevents the unit from becoming damaged, whether on a cargo vessel at sea or being used outdoors as a storage unit. The steel is easily modified too, so containers made from Corten are a great base for conversion projects: it can be cut down, painted and can withstand adding fixtures, such as doors and windows, without compromising the structural integrity. We proudly use Corten Steel for our shipping containers as it offers exceptional durability, corrosion resistance, and aesthetic appeal. Its ability to withstand harsh environmental conditions makes it a preferred choice for maritime applications, ensuring reliable performance and longevity. Corten Steel is also frequently used for outdoor projects and architecture. Famous landmarks, such as the Angel of the North in Gateshead and Broadcasting Tower at Leeds Beckett University, have utilised Corten Steel for the exterior of their buildings as it not only provides a strong, robust material to build with, but it also gives an aesthetically pleasing appearance that stands out against the landscape.
