Effect of Microstructures on Corrosion Behavior of Nickel Coatings: (I) Abnormal Grain Size Effect on Corrosion Behavior

Nickel coatings with different microstructures were synthesized by pulse jet electrodeposition technique. Their morphology and microstructure were investigated by scanning electron microscopy (SEM) and transmission electron microscopy (TEM). The corrosion property of the coatings was studied by using polarization, electrochemical impedance spectroscopy (EIS), potential of zero free charge (PZFC) measurements and Mott–Schottky (M–S) relationship. The results showed that the coating with grain size of 50 nm possessed higher corrosion resistance than that with grain size of 10 nm. This abnormal behavior may be related to the existence of nanoscale twins in the coatings and the lower concentration of acceptor in the passive films.