Model Solutions of Concrete Environment and Effect of Chloride Ions on the Electrochemical Corrosion Behavior of Reinforcing Mild Steel

Two model solution have been used in this study in order to simulate the corrosion behavior of mild steel rebars in the pore concrete environment. The first one is based on saturated calcium hydroxide (Ca(OH)₂, pH 12.7± 2) and cement (portland Type I) extract solution (pH 12.7± 2) in open air, at room temperature (24± 1°C). The effect of chloride ions (5g/l and 10g/l NaCl) was studied in both model solutions. Electrochemical techniques such as potentiodynamic polarization curves and electrochemical impedance spectroscopy (EIS) have been performed in a classical three-electrode cell. Also additional information was obtained by SEM and EDAX analysis. It seems that there is a difference in the way each solution simulates the behavior of steel, because the passive films formed show dissimilar topography, composition and anticorrosion protectiveness. The presence of chloride ions allows one to see more clearly the difference between the model solutions and the way each one interacts with the reinforcing steel. In this case the cement solution provides a more protective film for the reinforcing steel.