Weathering steel is a high-strength low alloy steel that was originally developed by United States Steel in the 1930s to resist corrosion and abrasion in their ore wagons. It was given the trade name Cor-ten and was first used in construction on the John Deere World Headquarters building in Moline, Illinois, which opened in 1964. Since then, the use of weathering steel has spread worldwide and in Europe, it is available as “structural steel with improved atmospheric corrosion resistance” and is a non-proprietary product. In suitable environments weathering steel forms an adherent protective rust ‘patina’, that inhibits further corrosion.
The corrosion rate is so low that bridges fabricated from unpainted weathering steel can achieve a 120-year design life with only nominal maintenance. Hence, a well-detailed weathering steel bridge in an appropriate environment provides an attractive, very low maintenance, economic solution. The first weathering steel bridge in the UK was a footbridge at York University in 1967 and the material was used for many bridges around the UK in the following 30 years or so. However, the use of weathering steel on bridges has increased significantly since 2001 when a former restriction on the use of the material over highways with less than 7.5m headroom was removed. It is now the material of choice for a wide range of bridge decks. This article highlights the benefits of weathering steel for bridges, describes the limitations on its use, and comments on both the material availability and the appearance of such bridges. It also provides advice on a range of issues including design and detailing, fabrication and installation, inspection and maintenance, and remedial measures, should corrosion rates exceed those anticipated at the design stage.
