Corrosion of Rebar in Concrete. Part IV. On the Theoretical Basis of the Chloride Threshold

Abstract A theory is developed for calculating the chloride threshold (CT) from the Point Defect Model (PDM). CT is defined as the ratio [Cl-]/[OH-] at which the passivity breakdown voltage (Eb) equals the corrosion potential, ECP. CT is sensitive to the T, ECP, pH, and Eb, because all four appear in the exponent X in CT = 10X. Small uncertainties in these parameters translate into a large uncertainty in CT, emphasizing the need for accurate T, ECP, pH, and Eb data. We demonstrate the theory by successfully calculating CT using data for selected systems.