The effect of hydrostatic pressure on the nature of passive film of nickel in 3.5% NaCl solution was investigated by means of polarization curves, electrochemical impedance spectroscopy (EIS), and Mott-Schottky measurement. The experimental results revealed that hydrostatic pressure had two opposite effects on passive film of nickel. On one hand, hydrostatic pressure improved the corrosion resistance of passive film of nickel such as the decreased acceptor density. On the other hand, the passive film became unstable and showed a higher diffusivity of acceptor density with the increasing of hydrostatic pressure, which deteriorated the corrosion resistance of passive film of nickel. The deterioration effect had greater influence on the passive film than the improvement effect, which led to the decreasing corrosion resistance of passive film with the increasing of hydrostatic pressure.

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