Atmospheric Corrosion of the Suspension Cables on the Williamsburg Bridge

The Williamsburg Suspension Bridge across the East River in New York City was opened to traffic in 1903. The four main support cables are composed of 7696 high carbon steel wires spun into 470-mm diameter cables. These wires were ungalvanized but given a protective organic coating when installed. The cables were inspected in 1980 and found to have undergone a significant amount of atmospheric corrosion. In 1982, wire samples up to 91 m in length were removed from the cables and the extent of atmospheric corrosion damage was evaluated. Mechanical properties experiments on corroded and uncorroded wires indicate that the atmospheric induced corrosion damage has degraded the load bearing capacity of the cable. An accelerated cyclic wetting/drying atmospheric corrosion test was used to estimate the current rate of corrosion induced damage. Based on these observations, it was concluded that the acidity and the chloride ion content in the New York City area precipitation, plus the graphite in the original organic coating, are the principal factors contributing to the atmospheric corrosion of the cables. Furthermore, the estimated current rate of corrosion confirms that some sort of cable rehabilitation or replacement is necessary.