Predicting Conditions in Coating Disbonded Regions on Buried Pipes in Nuclear Plants

Abstract Corrosion would not be a concern if the coating on a buried pipe is well bonded or completely intact (without holidays). The danger occurs when the coating is disbonded, has a holiday and shields cathodic protection (CP) current. The corrosion severity in the coating disbonded region is determined by the local environment and the ability of CP current to penetrate into the disbonded region. Unfortunately, the pipeline industry has so far been lacking field techniques or procedures for measuring the corroding conditions in a coating-disbonded region irrespective of the presence of CP. A model is developed that is capable of making predictions of the corroding conditions in the coating disbonded region, including chemistry, potential and corrosion rate. This model is built upon fundamental principles and reduced to simple algorithms that can allow for field application. This paper reports the model, the results and the techniques for field application.