Johannes Viertel

Effects of weld treatment methods on the performance of organic coatings during accelerated offshore cycle tests were statistically investigated. A full factorial design was applied to low‐carbon steel welds with imperfections and varying preparation methods (blast‐cleaning, mechanical grinding, laser‐based treatments). Laser treatment was evaluated as a supplementary method and as a stand‐alone approach. Surface preparation was the dominant investigated main factor influencing coating damage, with additional significant contributions from weld position, imperfection type, and exposure time. Preparation methods combining laser treatment with mechanical treatment performed equivalent to blast‐cleaning. Purely laser‐based methods, however, resulted in significantly higher damage levels. A key limitation of the 100 W ns‐pulsed laser process was the incomplete removal of silicate welding slag, leading to partial remelting and redeposition of glassy residues within weld grooves. The damage accumulation followed a two‐parameter Weibull model. Laser‐assisted weld preparation had the potential as an alternative to blast‐cleaning, provided that weld geometry is properly conditioned and laser parameters are appropriately scaled.

The growing global demand for renewable electric power sources is driving forward the errection of ever more offshore structures, such as wind energy plants (WEP) and switchgear platforms. Worldwide there are now over 200 000 wind turbines operating, with a total capacity of 432 000 Megawatt (MW) as of the end of 2015.¹ Offshore wind power capacity alone is expected to reach a total of 75 Gigawatt (GW) worldwide by 2020.² This increase in the number of installations goes hand in hand with the increased demand for maintenance and repair operations of the applied corrosion protection coatings. The corrosion protection coatings applied during the construction of these structures, is regulated by international standards, such as ISO 12944 and others. There is, however, no internationally recognised standardisation regarding off‐shore repair systems and their specifications, or application methods. Offshore work demands radically different materials and methods of application, compared to the original coatings and their application procedures. The research project RepaKorr,³ funded by the German Education and Research Ministry (BMBF), includes the development of a novel, single layer repair coating, especially suited for the offshore repair application.