Long-term Corrosion Protection of Pipelines by High Performance Polyurea Spray Coatings
Long-term exterior corrosion protection of buried pipelines is and remains a dominant factor influencing safety, performance, and cost for pipeline operators. There is normally more than one corrosion barrier applied to pipelines with a design life of 40 years or more. Cathodic Protection (CP) inhibits steel oxidation by creating an electrochemical cell vs. ground potential. The probability of oxidizing attack also is reduced by polymeric coatings which prevent direct contact of soil, water, or air with the steel pipe surface. Coatings used in the past often did not yield the lifetime originally expected. This has been reported for various materials from bituminous compounds to polyethylene wraps or thermoset epoxy or FBE coatings. Salt marsh soil, named “Subkha” in Arabic, provides a particularly challenging environment for buried pipelines . Subkha soils, found in coastal areas around the world, are sandy soils with high water and salt contents. Novel High Performance Polyurea spray coatings were developed that come close to being an ideal coating material for Subkha soils. These materials possess a high resistance to Subkha conditions, a very strong bond to the steel, and the shortest possible application and curing time. Hence, they are ideally suited for rehabilitation of aged pipelines in Subkhar soils. This presentation will describe these materials and test results from industry standard, lifetime prediction tests. And from a successful field test in Subkha environment.