Weathering steel is a high-strength, low-alloy steel originally developed by U.S. Steel in the 1930s for corrosion and wear resistance in mining cars. Known by the trade name Cor-ten, it was first used in the construction of the John Deere World Headquarters building in Moline, Illinois, which opened in 1964. Since then, the use of weathering steels has spread globally, and in Europe they are known as "atmospheric corrosion-resistant structural steels" and are a non-proprietary product.

In the right environment, weathering steel forms an attached protective rust "patina" which inhibits further corrosion. This patina is so low that bridges made of unpainted weathering steel can achieve a design life of 120 years with minimal maintenance. Therefore, in the right environment, a well-crafted weathering steel bridge is an attractive, economical solution with very low maintenance costs.

The first weathering steel bridge in the UK was a footbridge at the University of York in 1967, and over the next 30 years the material was used on many bridges throughout the UK. However, the use of weathering steel in bridges has increased dramatically since 2001, when previous restrictions on the use of weathering steel on highways with clearances of less than 7.5 meters were lifted. Weathering steel is now the material of choice for all types of bridge decks.