Investigating Oxide Film Degradation at Arkansas Weathering Steel Bridges

Abstract

Uncoated weathering steel (UWS) is used for bridges to minimize maintenance costs incurred due to possible steel corrosion. State highway departments often use weathering steel for bridges with the expectation that the weathering steel structure will not corrode. Weathering steel has improved corrosion-resistant behavior over conventional steel; however, weathering steel is not maintenance free and will corrode if not used in correct ambient conditions and properly maintained. Consequently, weathering steel retards corrosion but may require future restoration through cleaning and/or applying surface coatings. The Arkansas Department of Transportation (ARDOT) bridge inspection inventory includes 859 UWS bridges. Approximately 11% of these bridges have some level of oxide film degradation, AASHTO defect code 3430. These bridges are located throughout the state. Other states have also experienced this condition, resulting in state highway departments facing the dilemma of how to restore weathering steel sections that have experienced corrosion. This article reviews the extensiveness and severity of oxide film degradation at UWS bridges in Arkansas, the prevalence of UWS oxide film corrosion in other states, how oxide film corrosion progresses as a function of time, and remediation measures.