<p>This study provides new insights into the passivation behavior and growth mechanism of nickel-based alloy in a simulated deep-sea environment, with a focus on the effects of applied potentials and solution pH. To comprehensively elucidate the influence mechanisms of the experimental variables on the passive film formed on the nickel-based alloy surface, in situ electrochemical tests, x-ray photoelectron spectroscopy, and transmission electron microscopy were employed. The results obtained from these analyses demonstrate that the passive film exhibits characteristics of an n-type semiconductor and possesses an amorphous structure, where the film thickness decreases with increasing potential, leading to enhanced ionic transport through the film. A novel finding is that the increase in potential not only raises the CrO₃/Cr₂O₃ ratio but also significantly increases the oxygen vacancy diffusion rate, which accelerates the cation transport and reduces the corrosion resistance. Furthermore, the oxygen vacancies increase with pH due to enhanced hydroxyl ion adsorption, while the Cr₂O₃ content decreases, resulting in a less protective passive film.</p>