Corrosion and Fatigue Behavior of Steel for Offshore Wind Turbine Bolts

Corrosion tests were conducted on bolt steel 42CrMoA in the simulated service environment of offshore wind turbine bolts in the splash zone and atmospheric zone through alternating wet dry cycles of salt spray. The corrosion products were observed by scanning electron microscopy (SEM) and their elements were detected by energy dispersive spectroscopy (EDS). The morphology of corrosion pits was characterized by optical profilometer, and the fatigue crack growth after corrosion was studied by in-situ fatigue testing machine. The results show that in the cyclic salt spray environment with alternating dry and wet conditions, the corrosion mass loss per unit area of 42CrMoA steel and corrosion time exhibited a power function. There was a linear relationship between the surface roughness and corrosion time of 42CrMoA steel. The initiation and propagation of fatigue cracks were promoted by corrosion pits, and the expansion and merging of multiple cracks accelerated the fracture of the specimen, thereby reducing the fatigue life.