Studium korozních procesů na ocelových konstrukcích ovlivněných usazováním chloridů

Abstract

The processes of corrosion on the surface of structures located in the outdoor environment is affected by the action of atmospheric corrosion factors. Chlorides and sulfur dioxide in the air are the main corrosion stimulators influencing the corrosion processes on the steel surface. In the 70s and 80s of the last century, the concentration of sulfur dioxide in the air reached maximum values, after this period there was a widespread introduction of desulphurization units in the Czech Republic. At present, the chlorides belong between the main corrosion stimulators spreading on surfaces of structure from winter maintenance used on roads. Steels with increased resistance to atmospheric corrosion, so-called weathering steels can be used in selected cases as a suitable alternative to traditional corrosion protection based on the application of the coating systems. The development of corrosion products on structures designed from weathering steels can be significantly negatively affected if the structures are exposed to increased chloride deposition over a long-time period. For effective application of weathering steels as a structural material is therefore important to understand the dependencies between the corrosion processes, the characteristics of the microclimate around structures, and the design of bridges. The first part of the dissertation includes monitoring the deposition rate of chlorides and the development of the corrosion layer on selected bridge structures over a busy highway and over a railway in Ostrava. Measuring devices were placed at selected positions of the bridge structures. Experimental measurements performed on selected bridge structures allow to evaluate the influence of microclimate under the bridge structure on the intensity of chlorides spreading on the bridge structure, the influence of the position of placed samples within the bridge structure, the influence of surface orientation on chloride intensity and also to determine the relationship between corrosion layer characteristics and chloride deposition rates. The second part of the research involves monitoring the change in the intensity of chlorides depending on the change in distance from their source. For this purpose, experimental stands were placed in selected positions around the road I/11 in the village Hrabyně. Measuring devices for monitoring chloride deposition in accordance with the standard EN ISO 9225 and corrosion samples were placed on each stand. The obtained data make it possible to evaluate the effect of the change in the distance from the chloride source on their deposition rate.