Threshold Chloride Levels for Localized Carbon Steel Corrosion in Simulated Concrete Pore Solutions Using Coupled Multielectrode Array Sensors

Threshold chloride levels for localized corrosion of carbon steel material have been studied in three types of simulated concrete pore solutions: sodium hydroxide-potassium hydroxide (NaOH-KOH) with pH 11.6, calcium hydroxide (Ca[OH]₂) with pH 12.6, and sodium hydroxide-potassium hydroxide-calcium hydroxide (NaOH-KOH-Ca[OH]₂) with pH 13.3. The nonuniform corrosion rates of carbon steel were measured with coupled multielectrode array sensors (CMAS) when the chloride concentration was changed from 0.0005 mol/L to 1 mol/L in each solution. Open-circuit potentials were also measured from the coupling joint of the CMAS probes and electrodes made of rebar specimens immersed in the simulated pore solutions to verify the results from the CMAS probes.