Corrosion protection coatings play a significant role in the overall performance, integrity and lifetime of steel pipelines.
The paper describes the important selection criteria to choose the right PE or PP coating system for a pipeline project. Here not only the operating temperature, but especially the transportation distance for the pipes, the intermediate storage and installation-conditions and -climate play a major role.
An overview of existing polyolefin systems for onshore and offshore is given. This selection might also be influenced by the later applied field joint system as it may also require specific components of the system or specific tolerances.
The coating step is a very complex process with many influence factors and here one step is depending on the previous ones in a direct influence of the later quality of the corrosion protection system. It starts from the surface preparation of the bare, rusty steelpipes with gridblasting, via the cleaning steps to avoid dust, oil and grease residues or salt, heating the pipe to the right application temperature and matching the application windows of each the epoxy, the adhesive and the intermediate or top coat materials. Finally the right combination of quality testings performed and specified for the coatings should ensure, that the pipeline owner will get the level of quality, he has specified and paid for.
During the installation in the field, the pipes are welded to each other. The uncoated pipe ends, the so called cut back area, has to receive a durable protection and coating after welding. A chain is as strong as its weakest link – so there should be the same high focus on the performance level when selecting the field joint system. This is the area with the most detected problems after some years of operation.The majority of field joints are done by shrinksleeves or cold applied tape with rather low requirement level.
The paper presents two new, improved methods with fused field joint coatings with the aim to fulfil the level of the minimum requirements of the factory applied coatings.