Inspection and Maintenance of Weathering Steel Bridges

Weathering steel is commonly used as a cost-effective alternative for bridge superstructures, as the costs and environmental impacts associated with the maintenance/replacement of paint coatings are theoretically eliminated. The performance of weathering steel depends on the proper formation of a surface patina, which consists of a dense layer of corrosion product used to protect the steel from further atmospheric corrosion. However, the development of the weathering steel patina may be hindered by environmental factors such as humid environments, wetting/drying cycles, sheltering, exposure to de-icing chlorides, and design details that permit water to pond on steel surfaces. Early detection of deleterious corrosion is important to extending the service life of the bridge structure; however, established inspection procedures for weathering steel bridges are often not available to inspectors. This project assessed different inspection and testing techniques in order to evaluate the performance of the patina and/or the level of chloride contamination. A combination of visual inspection and tape testing was found to be the most practical and cost effective inspection methods that achieved objective, reliable and repeatable results. This study also developed a patina rating index for comparison of performance between different inspection cycles or between various bridges within an inventory. The patina rating index can also be used to prioritize general maintenance needs for a weathering steel bridge inventory.