Cathodic protection (CP) of carbon steel has been extensively studied for structures exposed to the open sea. However, the knowledge and data available for carbon steel cannot be directly applied to stainless steels, especially in the case of confined surfaces that are prone to crevice corrosion. In the context of stainless steels, confined surfaces (such as the contact surfaces of fasteners or valves) are critical zones as crevice corrosion represents the primary failure mode for passive alloys in seawater. With CP, the local potential achieved in confinement areas is highly dependent on various factors, including the actual geometries (crevice gap, length, local pH and Dissolved Oxygen (DO), ohmic drops, etc.). These factors can raise questions about the actual efficiency of CP if the current cannot reach the confined area. Conversely, if sufficient current can reach the confined area, the risk of hydrogen embrittlement (especially for strain-hardened or precipitation hardened alloys) should be taken into consideration. A specific experimental setup has been constructed to characterize the electrochemical behavior of stainless steel in a confined environment and the physicochemical properties of the confined seawater. The results have shown a complete deaeration of the confined seawater under all test conditions, along with an increase of the pH when CP is applied. The tests have also highlighted the significant impact of slight crevice gap variation on the current distribution. Based on the experimental findings, polarization curves representing confined environments have been generated. These curves have been integrated into a finite element model, allowing for the extrapolation of the experimental results to different crevice geometries. After a few centimeters, little to no current should be able to reach the confined surfaces if the crevice gap is inferior to 10µm. However, the risk of corrosion of stainless steels remains limited due to the local CP-induced chemistry at the interface. The CP also mitigates the ohmic drop in the confined area which also tend to reduce the risk of crevice corrosion. This work has enabled a deeper understanding of how cathodic protection prevents crevice corrosion on low-passive-grade stainless steels in natural seawater. It also provides additional information on the polarization behavior of stainless steels in confined areas on the crevice geometry.