Effect Of Hydrostatic Pressure On The Corrosion Behavior Of Pure Nickel

The effect of hydrostatic pressure (from 1atm to 90 arm) on the corrosion behavior of nickel at room temperature in 3.5% NaCl solution were investigated by means of polarization curve and electrochemical impedance spectroscopy (EIS) and Mott-Schottky and potentiostatic measurement. The experimental results revealed that the hydrostatic pressure had a strong influence on the corrosion process of pure nickel. With the increasing of hydrostatic pressure, the corrosion rate of pure nickel increased,the anodic process was accelerated while cathodic process remained unchanged. Hydrostatic pressure had two opposite effects on the anodic process of nickel. On one hand, hydrostatic pressure improved the corrosion resistance of passive film of nickel, such as the decreased acceptor density and the increased space layer thickness. On the other hand, hydrostatic pressure deteriorated the corrosion resistance of passive film of nickel. The passive film became unstable and showed a higher diffusivity. The deterioration effect had greater influence on the anodic process than the improvement effect, which lead to the decreasing of the corrosion resistance with the increasing of hydrostatic pressure. The pitting breakdown potential and induced time of pure nickel in hydrostatic pressures of latm and 80atm at room temperature were investigated by means of electrochemical measure method. The effect of hydrostatic pressure on the pitting breakdown potential and pitting generation mechanism of pure nickel was discussed based on the stochastic model. The experimental results revealed that the hydrostatic pressure had a strong influence on the pitting process of pure nickel, distinguished by the change of the pitting behavior and pitting mechanism. With the increase of hydrostatic pressure, the susceptibility of the birth of pitting increased, and the critical potential of pitting breakdown of pure nickel decrease obviously. With the increase of hydrostatic pressure, the pitting induced time of pure nickel becomes short, which is arributed to the change of pitting generation mechanism. With the increase of hydrostatic pressure, the stablbility of passive film on pure nickel decreased, and hydrostatic pressure deteriorated the corrosion resistance of nickel.