Investigation into Corrosion of Surface Treated Weathering Steel Bridges for More Than 30 Years

Abstract

In order to investigate the corrosion of surface treated weathering steel bridges constructed more than 30 years ago, we conducted a visual inspection, a measurement of rust and coating thickness, a measurement of ion transfer resistance, cross-sectional observation by the reflected polarized light and EPMA analysis. The rust appearances of 57 points out of 78 were assessed normal by the visual inspection. Imbricate and layer-delaminated rusts were observed at the some ends of the bridge beam from which water used to be leaking. The rank of the rust appearance tends to decrease with an increase in the thickness of rust and coatings. The cross-sectional observation and EPMA analysis revealed that the condensed Cl existed at the bottom of the anomalous rust, while the optically isotropic layer of protective rust existed at the bottom of the normal rust.