Stainless Steel vs. Cor-Ten® Steel

Stainless Steel vs. Corten Steel

Stainless Steel vs. Cor-Ten® Steel

Many types of steel corrode over time as they are exposed to the presence of water and oxygen, while others, like stainless steel and Cor-Ten Steel are considered corrosion-resistant steels. When selecting a corrosion-resistant steel, it’s important to understand how each of these differ. 

What is stainless steel? 

Stainless steels are steels containing a minimum 10.5 percent chromium and less than 1.2 percent carbon and other alloying elements. The chromium oxidizes quickly to form a protective, or “passive,” layer of chromium oxide on the metal surface. This oxide layer resists corrosion while preventing oxygen from reaching the underlying steel. The more chromium that is added to the steel’s composition, the more stable the oxide layer becomes, which enhances its corrosion resistance.

Other elements such as nickel, manganese and molybdenum can also be added to enhance stainless steel corrosion resistance. The steel’s surface must be exposed to oxygen in order for the protective layer to form. Corrosion resistance is greatest when the steel is boldly exposed and the surface is maintained free of deposits. However, certain chemical environments can disrupt this protective layer and initiate corrosion. So, while stainless steel is highly resistant to corrosion, it is not immune to corrosion in all environments. 

Stainless steel plays a prominent role in many industries, including energy, transportation, building, medicine, food and logistics, and can also be found in and everyday objects, such as  cookware, kitchen utensils and cutlery. Stainless steel’s strength, 100 percent recyclability, corrosion resistance, mechanical efficiency, and low maintenance characteristics make it an ideal material for all kinds of applications. 

What is Cor-Ten® steel

Cor-Ten® is the United States Steel Corporation’s (USS) trade name for atmospheric corrosion-resistant steel. It was developed to be used where higher strength and longer life cycle material were desired. Today, the terms “COR-TEN®,” “cor-ten,” “corten” and “weathering steel” are used interchangeably when referring to atmospheric, corrosion-resistant steels. 

Weathering steels are a family of ASTM specifications, as well as several trademarked specifications (including Cor-Ten®) exhibiting similar corrosion-resistant properties. Weathering steels are high-strength, low-alloy steels with a carbon content of less than 0.2 percent, which produces adequate formability and weldability. Most weathering steels are also composed of manganese, phosphorus, sulfur, silicon, nickel, chromium, copper and vanadium. Weathering steels have a tensile strength of 70 ksi and a tensile yield of 50 ksi.

Similar to stainless steels, the fundamental benefit of weathering steel is its ability to resist corrosion. Weathering steel naturally forms a protective layer of rust, called the patina, when exposed to various atmospheric conditions. This patina layer regenerates continuously as it is exposed to wet and dry cycles to guard this material against future corrosion. Essentially, weathering steel is allowed to rust in order to form the protective patina coating, which results in a much lower corrosion rate compared to stainless steel.

Advantages of Cor-Ten® and weathering steels

In addition to its corrosion resistance, weathering steel offers more advantages, such as: 

  • No painting needed: The corrosion resistance of weathering steel enables it to be used unpainted in structural and architectural applications, which minimizes construction costs and duration.  
  • Minimal maintenance: Periodic inspection and cleaning should be the only maintenance required to ensure the weathering steel bridge continues to perform well.
  • Aesthetic appeal: The unpainted appearance of weathering steel blends well in gardens, backyards, parks, and other outdoor environments where bridges are required. 
  • Environmental benefits: The environmental problems associated with volatile organic compounds (VOC) from paint and the disposal of blast-cleaning debris from future maintenance work are avoided, making weathering steel a sustainable solution
  • High temperature benefits: Oxidation loss of steel at temperatures above 400 degrees Celsius can be decreased by using weathering steels. At these temperatures, a patina forms even in the absence of water. The precise performance improvement is dependent on the heating cycle and environmental conditions. A typical improvement would be an increase of 50 degrees Celsius over equivalent loss in carbon manganese steels.

Contact Central Steel Service, Inc. for Cor-Ten®  and Weathering Steels

Central Steel Service stocks high strength, high strength weathering steel across all product categories to meet the needs of our customers. We understand that the unique applications requiring these specialty products require the utmost attention to quality and material traceability. By focusing our entire resources on supplying only these specialty products, we can give you complete confidence in your decision to allow us to service your steel requirements. Contact an experienced sales representative at Central Steel Service to learn more about our company and products.