2006 Volume 55 Issue 2 Pages 75-81
To elucidate the local wet atmospheric environment surrounding a weathering steel girder of bridge in a mountainous region, atmospheric temperature, relative humidity near on steel surface and steel surface temperature were measured by a monitoring device at each site simultaneously for two years. The time of dew condensation (TOC) at the six sites was calculated from the above data. To compare the obtained TOC to the characteristic of the rust, the rust layers formed on the representative sites were characterized by XRD, electrochemical potential of steel with rust layer, rust thickness and observation of the surface appearance, respectively. The obtained values of TOC at all sites were less than 10% of the time of wetness (TOWISO) according to ISO 9223. These low levels of the TOC corresponded to the thin thickness of the rust layers. The values of TOC also affected to the mass fraction of γ-FeOOH constituent, the potential and the surface appearance. In this case on the local site of the bridge girder in a mountain region, it was concluded that the TOC was a better indicator for wet atmospheric environment than the TOWISO.