Corrosion behaviors of TiN and Ti-Si-N (with 2.9Â at.% and 5.0Â at.% Si) coatings by electrochemical impedance spectroscopy

TiN and Ti-Si-N (2.9 at.% and 5.0 at.% Si) coatings were fabricated on the surface of polished Si (100) wafers and stainless steel substrates by cathodic arc ion plating. The XRD results showed that the preferred orientation of the TiN crystals changed from TiN (111) to TiN (200) with an increasing silicon content. The TiN coating exhibited a polycrystalline structure with an average grain size of approximately 18 nm, while the Ti-Si-N coatings exhibited a nanocomposite structure of TiN nanocrystals embedded in amorphous Si3N4. In electrochemical impedance spectroscopy (EIS) tests, the amorphous Si3N4 phase distributed on the boundaries of the Ti-Si-N (5.0 at.% Si) coating and acted as an effective barrier layer against the penetration of the corrosion solution, which resulted in better corrosion resistance compared with TiN and the lower-Si-content Ti-Si-N coating (2.9 at.% Si). Immersion tests and surface morphology observations of the samples after corrosion were also carried out to investigate the corrosion mechanism and behaviors of TiN and Ti-Si-N composite coatings.