Avaliação da corrosão do aço carbono S355 em água do mar para aplicação em fundações de turbinas eólicas offshore

Abstract

The participation of offshore wind energy in the Brazilian energy matrix is an increasingly close reality. Although there is still no offshore wind farm in operation on the Brazilian coast, the vast potential has already been pointed out, highlighting the on the coast of Ceará, due to the excellent wind index. Monopile offshore wind foundations represent the most common design and the steel most used in the manufacture of these support structures is carbon steel S355. These structures are exposed to the marine environment , so corrosion of this material is a complex and expensive problem in offshore maintenance . Therefore, the objective of this research was to evaluate the corrosion resistance of S355 carbon steel in seawater, which was collected in the metropolitan region of Fortaleza, Ceará The investigation of the steel corrosive process was conducted using gravimetric tests and electrochemical tests: Open Circuit Potential O C P ), Potentiodynamic Polarization (PP) and Electrochemical Impedance Spectroscopy ( EIS). The immersion test was performed in triplicate, and the mass loss was obtained to determine the cor rosion rate after 24 hours and 45 days of immersion. The OCP monitoring of the and the evolution of the EI S diagrams were carried out for up to 96 hours of immersion, with a decrease in the capacitive arcs being observed with the increase in the immersion time, reducing the resistance to polarization. Additionally, in the course of immersion time, the potential values became more negative. All these indicators characterize the corrosion of the material in seawater. The surface morphology of the samples afte r the corrosion tests was characterized using Optical Microscopy (OM). The presence of uniform and localized corrosion was identified. The corrosion products formed on the surface of the samples were characterized by X Ray Diffraction and Mössbauer Spectro scopy. Magnetite (Fe 3 O 4 ) and lepidocrocite γ FeOOH) were identified, the latter being predominantly observed. Finally , the aggressiveness of the corrosive process was classified as moderate. Based on the results obtained , it is concluded that for the application of S355 steel in foundations of offshore wind turbines, it is recommended to choose a cathodic protection system (PC), in order to mitigate corrosion. Highlighting the importance of advancing research in the area, directly contributing to the functionality and safety of operations in wind energy generation structures in such a challenging environment.