Analysis of microbially induced iron corrosion inside monopiles of offshore wind turbines - methods for in situ experiments

Offshore wind turbines are exposed to extreme environmental conditions inside monopiles where microbially induced corrosion (MIC) occurs. In this study, microbial in situ incubation experiments were carried out at different water depths inside a monopile. First results indicate that water depth-related seasonal stratification of the inner water column clearly influences microbial consortia and the grade of corrosion. At a water depth of 6 m, iron-oxidizing microbes dominate under aerobe conditions, while sulphate-reducing and methanogenic microbes are prevailing close to the sea bed at 21 m in temporarily anoxic and sulfidic bottom water. The S355 steel specimens show significant corrosion after several months of in situ incubation, however pronounced pitting was not observed. The focus of this study is the development of long-term in situ observation methods of MIC inside offshore monopiles to finally test adapted corrosion mitigation strategies.