Corrosion behavior of nanostructured Ni-Si3N4 composite films: A study of electrochemical impedance spectroscopy.

Ni-Si₃N₄ nanocomposite films with both the consecutive Ni crystallites and dispersed Si₃N₄ particles in the nanometer range have been fabricated using DC electroplating technique, and characterized by scanning electron microscopy (SEM), transmission electron microscope (TEM), and X-ray diffraction (XRD). The corrosion resistance of the Ni-Si₃N₄ nanocomposite film has been compared to that of pure Ni coating through polarization. Meanwhile, the corrosion process of Ni-Si₃N₄ nanocomposite film in neutral 3.5% NaCl solution has been investigated using electrochemical impedance spectroscopy (EIS). The results show that the Ni-Si₃N₄ nanocomposite film is more resistant to corrosion than the pure Ni coating. The corrosion of Ni-Si₃N₄ nanocomposite film is controlled by electrochemical step, and the whole corrosion process is divided into two sequential stages. The main corrosion type of Ni-Si₃N₄ nanocomposite films in neutral 3.5% NaCl solution is pitting. [ABSTRACT FROM AUTHOR]