Evaluation of Dry Film Thickness Data for Assessing Field Performance of Uncoated Weathering Steel

• Nia Spears, Civil Engineering, University of Missouri
• Tiana Noelani Thorp, Civil Engineering, University of Delaware

• Jennifer McConnell, Civil and Environmental Engineering, University of Delaware

Uncoated weathering steel (UWS) was introduced to the United States bridge market in 1964 and has the potential to be better for the environment because of the lack of the need for a paint layer, which removes the release of volatile organic compounds into the atmosphere and the disposal of removed paint. But there are still questions surrounding how well it performs. Corrosion of steel structures has been a problem for years, and there has been no way to fully evaluate how long it takes for this corrosive layer to be detrimental to the performance of a steel structure. There are conclusions as to what makes UWS more at risk for corrosion, but there is still no quantitative method to rapidly evaluate UWS in field situations. Dry Film Thickness (DFT) could be the answer since the gauges are inexpensive and travel sized. Dry film thickness data collected from in-situ bridges was evaluated to see how reliable the data could be in quantifying the performance of a bridge. Twenty-one bridges were categorized into good and inferior bridges. On each bridge, measurements were taken, in microns, in 12 different locations. Out of those 12 locations, five locations, intended to represent the extremes in performance, were closely looked at to identify any present trends in the data. When evaluating the bridges individually, the data matched the original hypothesis that the good performing bridges would have a lower DFT average, but when dissected, some overlap in the good and inferior bridges was revealed leading to further investigation. This overlap in the data could be caused by the environmental factors that the bridges are exposed to.