Coating Condition Monitoring and the Practical Application

Abstract

Corrosion is a main source of degradation of most offshore and ship structures. Especially ballast tanks are vulnerable to corrosion. Protection is pro-vided by coating systems, postponing the onset of uniform corrosion. It is there-fore essential to have a coating system in place and intact. Inspecting ballast tanks for the integrity of the coating system is an operational challenge. The improve-ment is to detect coating degradation before the corrosion process starts and only enter when it is required. Within the European project SAFEPEC [1], it has been reported that continu-ous inspection of the condition of the coating system helps improving the relia-bility of the structure. Hoogeland et al. [3] described a coating condition moni-toring system that uses electrochemical measurements, i.e. the electrical current between steel to be protected and an anode. This paper demonstrates the reliabil-ity of the monitoring system by experimental validation using a Bayesian ap-proach. A long term measurement campaign has been performed on board a vessel. Inside a ballast tank, specimens are attached and intermittently exposed to sea-water. The electrical current between these plates and the anode are measured over about two years. The measurements are analyzed and based on the results, the condition of the coating of the installed specimens is predicted. By showing the actual status of the specimens, the reliability of the system is shown and the applicability for wider use is explained