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Blended cements are today commonly used for concrete structures built near the sea. When reinforced concrete is exposed to the atmospheric marine environment, it is necessary to consider steel corrosion caused by both, chloride ions and carbon dioxide. In this research, reinforced OPC and FA cement concrete samples have been tested in order to evaluate their comparative performance when exposed to chlorides, to CO2 and to both agents acting together. The techniques used to evaluate the steel corrosion rates have been the polarization resistance, intersection method of polarization curves, and electrochemical impedance spectroscopy. The results indicate a similar behavior of FA and OPC concrete for samples exposed to CO2. For the pure chloride exposure and the combined exposure regimes, the behavior depends on the type of binder. The polarization resistance technique appears to show some limitations when there is not enough electrolyte inside the pores.