Abstract
The technical-economic optimization of pipeline coatings in association with cathodic protection is a permanent objective for petroleum operators. The paper describes the author’s company experience and current choices for the pipeline coatings used in offshore operations. Performance and failure cases of the various types of coatings are described, including for risers. Polyethylene and polypropylene based three-layer coatings are most often used for plant-applied coatings of pipes. Polychloroprene and glassfiber reinforced epoxy are the main systems used for risers. A special care has to be paid to field joint coatings. Types and materials of pipelines and risers, laying techniques and maximum operating temperature are parameters influencing the selection of these coatings. In spite of possible coating damage, no corrosion has been identified in the submerged zone due to cathodic protection efficiency in sea water, even under disbondments which may cause corrosion due to “cathodic shielding” in the case of onshore buried pipelines. The most critical zone for offshore pipelines is the transition area between riser thick coatings and atmospheric paint system where accelerated corrosion may occur. Important efforts are currently produced in the field of International Standardization (ISO) for specifying the best compromises for pipeline coatings.
