Abstract—This study investigates the impact of using 50% Ground Granulated Blast-Furnace Slag (GGBS) as a cement replacement on corrosion resistance and compares different measurement techniques for assessing corrosion. Electromigration method was employed to simulate chlorideinduced corrosion in RC samples with GGBS. The study used Electrochemical Impedance Spectroscopy (EIS), Linear Polarization Resistance (LPR), and Galvanostatic Pulse (GP) measurements to monitor corrosion current (Icorr) over time. Results show that LPR generally indicates higher and more variable Icorr values compared to GP, which tends to provide more stable readings. The size of the chloride solution reservoir also affects corrosion rates, with larger reservoirs leading to higher Icorr due to increased chloride availability. The findings emphasize the vital impact of measurement methods and experimental settings on assessing concrete reinforcement durability, underscoring the importance of comprehensive evaluation strategies to accurately characterize corrosion behaviour.