Here we aimed to electrochemically characterize a zinc-rich epoxy nanocoating primer (ZREP), as well as a composite variation incorporating carbon nanotubes (CNT-ZREP), on an API X52 pipeline grade steel substrate. A rotating cylinder electrode (RCE) was used to incorporate the flow regime and equivalent shear stress conditions. The selected electrolyte for testing was 3% (wt.) NaCl saturated with CO2. The anti-corrosion properties of these nanocomposite coatings are a result of the combined effects of Zn and C nanoelements, which impart special properties not initially inherent in the matrix or in the nanoelements. The effects of these medium conditions on the performance of the substrate/coating system were characterized in real-time by electrochemical impedance spectroscopy. The damage evolution concept was adopted to analyse the current stages and to propose possible mechanisms for the roles of the CNTs and Zn cathodic in providing enhanced protection to the substrate.