A laboratory study on the atmospheric corrosion of nickel in NaCl solutions during cycling wet-dry conditions

The polarization resistance of nickel subjected to NaCl solution during wet/dry cycling conditions was monitored using an EIS impedance technique. The influence of relative humidity (RH), temperature, surface orientation and length of wetting period on the corrosion process of nickel is described. The average mass loss per wet-dry cycle (AML) was calculated during the exposure. The nickel plates corroded more substantially on the upward direction than those on the downward direction. The corrosion mass loss of nickel increases with increasing RH, temperature and length of wetting period. The corrosion process of nickel is anodically controlled by nickel dissolution during a full immersion in NaCl solution and cathodically controlled by a reduction of oxygen under thin electrolyte layers during the drying period. The corrosion rate of nickel decreases rapidly during the initial stages of exposure. It then decreases slowly and eventually attains the steady state during the last stages of exposure.