Theoretical models for pitting potential (Epit) and self-corrosion potential (Ecorr) were established based on the pitting nucleation mechanism and steel polarization theory, respectively. Based on corrosion thermodynamics, the critical chloride content (Ccrit) was defined as the chloride content at which Epit is equal to Ecorr, and a theoretical model for Ccrit was proposed. The results indicate that Epit exhibits a negative linear correlation with the logarithm of chloride content. An increased chloride content decreases Ecorr by causing a negative shift in the anodic polarization curve. Ccrit varies exponentially with Epit, Ecorr, temperature and pH value, small variations in the four parameters can be magnified as large variability in Ccrit, which partly accounts for its significant scatter in the literature. For a typical temperature of 298 K and a pH value of 13.5, the benchmark value of Ccrit (expressed as [Cl-]/[OH-]) is 1.41.