The objective of this study was to explore the corrosion performance of major microstructures (including ferrite, pearlite, bainite, and martensite) presented in pipeline steels (in a simulated CO2-saturated aqueous phase). Commercially available carbon steels were transformed into monolithic single-phase samples through appropriate heat treatment for the corrosion study. The corrosion susceptibility of each produced microstructure was identified using potentiodynamic polarization measurements. The four microstructures exhibit noticeable differences of electrochemical behavior in the environment. At open circuit potential, pearlite exhibits the lowest corrosion rate, whereas ferrite has the highest corrosion rate. The preliminary results are discussed regarding the merit of this approach to advance the mechanistic understanding of how pipeline steels corroded in such a specific environment.