The high basic environment created by concrete pore water protects the reinforcing steel from spontaneously corroding. Chloride ions destroy the passivity of steel in concrete and the steel spontaneously corrodes in moist concrete. A corrosion deterioration model is described as the sum total of time periods for the structure to reach its end of functional service life. The two time periods are the time to initiate corrosion at reinforcing steel depth equivalent to the end of functional service and the time to spalling of the concrete. The deterioration model may be used to estimate the service life and remaining service of concrete structures exposed to chloride environment. The case of concrete bridge decks is used as an illustrative example.