Aspects of Modern Corrosion Protective Coating Technology
Proceedings Publication Date
Michael Schad
Michael Schad, Dr. Oliver Zipffel
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Corrosion protective systems- e.g tapes, shrink sleeves and liquid coatings ( polyurethane and epoxy) have been used for decades on all types and sizes of buried pipelines. Results thus obtained are as versatile as the available range of products and systems. This session deals with the material properties and practical experiences of the most common systems to ensure a long term performance of corrosion protection. Technical properties of corrosion protective coatings are described in national and international standards-like ASTM standards and DIN EN guidelines. Buried steel pipes for the transport of liquid and gaseous media are protected against corrosion by coating with thermoplastic material or thermosetting compounds. While coating of the pipe is made in the factory, some parts of a pipeline remain   that have to be coated on the construction site. Depending on pipe laying method employed, trenchless or in open trench, only welded joints or also bends, valves, T-pieces and flanges have to be protected in the field. The ideal is to achieve an equal technical performance level of standard factory coatings and field coatings thus providing an unbroken  chain of quality and security. In fact the resistance for load stresses and peel forces of  three layered PE-or PP factory coatings exceeds the performance level of standard field coatings by far. The different performance level originates from the general demand for easy on site applicability, which makes it necessary to accept lower level of mechanical strength in case of field applied tapes and shrink sleeves.

State of the art three-ply- self-amalgamating plastics tape coatings and 3-ply shrink sleeves have proven their high technical quality on innumerable sites worldwide during the last twenty years. In case of changing weather conditions or in cold or windy climate tape coating systems have to be preferred due to their wide range of application from – 40° to  60 °C . The choice of the appropriate coating system depends significantly from weather and general circumstances on site. e.g. high durable liquid coatings react very sensitive on moisture and cold temperatures.

Irregularly shaped geometries as flanges or valves request for other solutions as standard pipe joints. A reliable corrosion prevention coating is achieved by use of permanently plastic petrolatum-based materials and additional mechanical protection by rockshields based on polypropylene fibres . If a highly resistant corrosion protection is requested,  a two component polyurethane brush compound is particularly suitable for field coating of irregularly shaped  installations. In case of trenchless pipe laying- as thrustboring and horizontal directional drilling, materials are stressed particularly by abrasion and shear forces and have to withstand highest corrosive and mechnical stresses. These requirements will be ensured by choosing two-components duroplast coating system based on polyurethane , GFRP or epoxy material). It pays off to specify a high quality coating system and to choose the appropriate system for the unique project requirements on site. It has to be taken into consideration while figuring up the costs for a project , that the percentage for joint coating  is around 0,03% of the total project costs only, but not choosing the best suited coating system can originate indirect loss and high consequential damages.
Appropriate high quality coating systems will  offer a durable and high performing solution in preserving pipeline values for decades to come.

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