Effect of Microstructures on Corrosion Behavior of Nickel Coatings: (II) Competitive Effect of Grain Size and Twins Density on Corrosion Behavior

Nanocrystalline nickel coatings with grain size of 50 nm were annealed in vacuum at 200 °C and 400 °C for 10 min. Their microstructures were investigated by transmission electron microscopy (TEM). And their corrosion behaviors were studied by means of polarization and electrochemical impedance spectroscopy (EIS). The results showed that their grain size grew up to about 60 nm (200 °C) and 500 nm (400 °C), respectively. The specimen annealed at 200 °C possessed higher density of twins in compared with the counterparts of as-deposited and annealed at 400 °C. The normal grain size effect on the corrosion behavior was not observed. However, it was found that the corrosion resistance of the coating linearly changed with the density of twins.