The free Cl- diffusion law, binding Cl- capacity and long-term reliability of electrodes in concrete were investigated under the effects of carbonation. Results reveal that the diffusion of free Cl- in concrete with and without carbonation adheres to Fick’s second law. Reducing ratio of water to binder and adding mineral admixture can decrease the free Cl- diffusion coefficient. Although the ability of carbonation to resist the penetration of Cl- is stronger than that to promote Cl- erosion, concrete after carbonation has a higher risk of initiating steel corrosion. Improving the reliability and decreasing the cost of electrodes requires more research.