Effect of Chloride Ions on Corrosion Behavior of High Tensile Strength Steel Rebar in the Synthetic Concrete Pore Solution Prepared with Tap Water

In this work, the electrochemical corrosion behavior of carbon steel grade 80 (with a minimum yield strength of 550 MPa) was studied in a simulated concrete pore solution containing chloride ions at different concentrations. The solution was prepared with tap water and contaminated with chloride at concentrations of (0, 0.5, 1, 1.5, and 2% as weight percent). Three electrode system was used in the electrochemical measurements. All the measurements were done at room temperature of (25 ±1 °C). Open circuit potential, Tafel extrapolation plot, and cyclic potentiodynamic polarization were utilized in this study. The surface morphologies were investigated by using an optical microscope and Scanning Electron Microscope supplied with Energy Dispersive X-Ray (EDX) Analysis. The results showed that the corrosion potential shifted in a noble direction (from -400mV to -350mV) and the corrosion rate of the steel samples increased (from 0.347μm/y to 0.519μm/y) with the addition of 1% NaCl. Then the potential shifted in an active direction of (-392mV) and the corrosion rate was decreased by (12.3%) with the addition of 2% NaCl, due to the reduction of dissolved oxygen with increased chloride concentration, and the effect of the barrier layer that formed. In addition, the cyclic polarization showed metastable pitting corrosion on the steel surface at the addition of 1% NaCl, and loss of the passivation layer at 1.5% NaCl with the formation of stable pitting corrosion. The critical chloride level was 0.5% NaCl addition. The EDX indicates that corrosion occurs at MnS inclusions sites. © 2023 School of Science, IHU. All rights reserved.