Corrosion fatigue is arguably one of the biggest scientific challenges in various technological sectors, leading to catastrophic failures on a regular basis. The degradation of materials due to the simultaneous effects of the environment (corrosion) and cyclic loading (fatigue) involves two damage mechanisms that are very complex on their own and, individually, not yet fully understood. An important area affected by corrosion fatigue is offshore wind turbine foundations, which are exposed to high-cycle fatigue loading, while being affected by corrosion due to seawater. We present a multi-phase-field modelling framework for high-cycle fatigue in salt-water conditions. The suggested model couples a corrosion description with a recent high-cycle fatigue model, including phase-field descriptions of the electrolyte solid interface and the mechanical fracture process. It allows to account for typical fatigue phenomena, such as mean-stress dependence and the slope of the S-N curve, as well as for corrosion related impact on fatigue, such as time-dependent behaviour and the loss of the endurance limit in corrosive environments. It naturally incorporates the transformation of corrosion pits into cracks and employs a moving boundary condition to describe electrolyte flow into mechanically formed cracks. The study aims to gain a more accurate and quantitative understanding of the detrimental effects that corrosive environments have on the fatigue life of steel components. Therefore, the proposed model is fitted and validated against corrosion fatigue experiments from the literature. We show that the model accounts for degradation effects on the fatigue life in corrosive environments by simulating S-N curves, and that it can predict an acceleration of crack growth rates by Paris-law type simulations.