Session: RIP: Predictive Modeling and Characterization of Corrosion Processes in Complex Environments (In Honor of Professor Digby Macdonald) (Part IV of IV)
A Practical Method for Predicting Coating Durability Using Portable EIS and Water Uptake (RIP2026-00064)
Portable electrochemical impedance spectroscopy (EIS) provides a mechanistically grounded yet highly practical approach for assessing the evolution of coating barrier properties under real environmental and operational conditions. This work presents the principles and application of a two-electrode, surface-mounted EIS method compliant with EN ISO 16773 and ASTM D8370-22, enabling rapid, repeated low-frequency impedance measurements (log Z at 0.1 Hz) without damaging the coating. Using a quasi-solid-state electrolyte interface, the method is applicable to dry coatings, laboratory panels, free films, and field-exposed structures of complex geometry, including pipelines, tanks, offshore assets, and industrial facilities. The approach resolves reversible physicochemical processes—such as water uptake, polymer plasticization, and temperature-dependent dielectric relaxation—as well as irreversible degradation marked by increased permeability, porosity development, and adhesion loss. Coupling low-frequency log Z with short automated water-uptake measurements allows quantitative classification of barrier performance and enables early detection of changes not visible during routine inspection. Laboratory studies confirm that this combination provides clear barrier ratings and fast, side-by-side comparison of coating systems and application methods. Findings from long-term 3-year exposure demonstrate that coatings with stable or recoverable impedance values exhibit long service life, whereas persistent impedance decline signals the onset of premature failure—often well before visible defects appear. Finally, machine-learning interpretation of impedance spectra maps degradation trajectories, groups coatings based on spectral similarity, and supports automated report generation from calibration datasets. Together, these capabilities establish a unified, quantitative framework that links polymer structure, environmental stressors, and long-term coating durability while providing actionable, field-ready decision support for coating selection, inspection quality, and asset integrity management.
