In this work, a warning system for monitoring the service status of organic coatings over large areas was developed. Taking advantage of electrochemical impedance spectroscopy (EIS) measurements, an attempt was first made to verify the repeatability of measurements made on surfaces with gradually increasing size. A threshold value of normalized impedance modulus was then set to be an easily detectable warning signal for the testing and maintenance of protective organic coatings. Monitoring continued for nearly two years, validating the threshold value for long immersion times. It was verified that the introduction of a defect could be easily detected through this system. Introducing a number of disturbing factors into the measurement did not significantly affect the results. Finally, the use of a portable potentiostat was adopted. It was found that the use of a potentiostat with smaller size but lower sensitivity equally allowed discerning the state of protection of the organic coating, with the possibility of using the measurement system for monitoring coated surfaces used in the naval industry.
