The world is currently in a severe man-made climate crisis, creating the need for using renewable energy sources such as offshore wind farms. Offshore wind turbines do not take up any valuable space on land and can use the greater wind resource at sea. The downside is, however, that they are exposed to a much harsher environment at sea, which could result in more failures and also lead to a smaller accessibility window for maintenance and repair. The structural components of offshore wind turbines are subjected to a corrosive environment and are exposed to cyclic loads that come in the form of wind and waves, which can cause significant corrosion and fatigue damage. Having accurate numerical models that can capture the physics of these damage processes could help reducing uncertainties on the structural performance of these components and therefore improve the position of offshore wind energy as a competitive renewable energy source. In this thesis, two such models are developed