Electrochemical and corrosion behavior of steel rebars in concrete exposed to industrial SO2 and CO2 environment

Abstract

Investigation into the corrosion mechanism of steel rebars in concrete under the combined influence of SO2 and CO2 is crucial for addressing the corrosion issues in reinforced concrete structures exposed to industrial environments. This study investigated the electrochemical and corrosion behavior of steel rebars in concrete under the combined influence of SO2 and CO2 using electrochemical methods, pH and SO42- concentration tests at the concrete/steel matrix interface, and surface analysis. During the corrosion process, a competitive chemical reaction between SO2 and CO2 occurs. The electrical resistance (Rc) of the concrete cover layer undergoes initial rapid growth, followed by slower increments, and then another period of rapid growth before eventually stabilizing. However, Rc sharply decreases over time, corrosion-induced damage in the concrete cover layer. CO2 diffuses to the vicinity of the rebar before SO2, inducing rebar depassivation. As rust severity increases, significant changes in the rust products are observed, with Fe(III) compounds transforming into Fe(II) compounds, and FeSO4·4H2O and FeSO4·7 H2O are prevalent in the rust products. Furthermore, the formation of ferrous sulfate compounds can lead to local acidification, thereby accelerating the corrosion rate, and hastening the aging and deterioration of the structure, posing a serious threat to the safety of the building structure.