The Study of Metal Corrosion Resistance near Weld Joints When Erecting Building and Structures Composed of Precast Structures

Abstract

Corrosion processes of the most common steel grades in various environments are the subject of numerous studies. At the same time, the corrosion of welded joints hidden in concrete thickness has not yet been studied. The authors set themselves the task of investigating this process. For this purpose, the corrosion resistance of several metals (grade St.3, U7 and their weld joints) was studied in standard test solutions, simulating a concrete pore liquid, containing sodium carbonates and hydrocarbonates, and sodium chlorides. Data on comparative corrosion resistance in saline media for specified materials were obtained. It was shown that the corrosion rate depends on the ease of CO2 ingress into the solution, and, to a lesser degree, on the metal microstructure. The surface character of the metal samples and the composition of corrosion products were investigated by scanning electron microscopy and an X-ray diffraction analysis. Chemical forms of surface compounds were determined. For the first time, it is clearly shown that the electrode coating flowing during welding does not always protect the weld from corrosion, as was previously believed. The corrosion rate, in this case, is just the same as at the surface of the metal plate of a similar composition. In the conclusion of this work, it is emphasized that in the case of alkaline and chloride-containing media, the protective coating falling from the electrode to the weld does not protect it sufficiently from corrosion.