As the first line of defense, protective coatings in harsh environments experience localized attack through various mechanisms. These shifts are largely driven by moisture penetration and reactions between the coating and environmental species. When cathodic protection (CP) is used to reinforce the coating/pipeline system, the rate of coating degradation can be influenced compared to conditions without polarization, raising concerns about long-term durability. This work explores the initial degradation pathways in fusion-bonded epoxy (FBE) and coal tar enamel (CTE) coatings commonly used for pipeline systems. The first part of the study examines how water absorption and hydrolysis affect the physical and electrical properties of the coatings. Immersion testing combined with Electrochemical Impedance Spectroscopy (EIS) and Local Electrochemical Impedance Spectroscopy is used to track changes in coating resistance and capacitance that indicate swelling, softening, and chemical breakdown of the polymer network. These measurements help identify the point at which water ingress begins to compromise coating performance significantly. The second part evaluates cathodic disbondment under applied cathodic potentials. By monitoring blister formation and adhesion loss, the study aims to understand how different coating types, thicknesses, and solution chemistries influence the rate and extent of disbondment. Particular attention is given to how the coating–substrate interface weakens during prolonged polarization. Finally, computer modeling is used to simulate and explain the experimental data obtained.
