Effect of Microstructure on the Corrosion Behavior of TiN Coatings

Abstract

In this paper, the corrosion properties of AISI 301 stainless steel (SS) coated with 1-micron thick titanium nitride (TiN) hard coatings is investigated. TiN was deposited by pulsed magnetron sputtering resulting in different microstructure ranging from agglomerated crystallites to homogeneous film. Microstructure of the coatings was characterized by scanning electron microscopy (SEM), x-ray diffraction (XRD), and energy dispersive spectroscopy (EDS). Resistance to general and localized corrosion was evaluated by potentiodynamic polarization in NaCl 1% solution. It has been shown that the existence of columnar structure in the TiN film reduces significantly the resistance to localized corrosion due to infiltration of liquid through paths at the grain boundaries. Furthermore, by comparing the polarization curves of TiN coatings deposited on SS and glass, it was shown that the electrochemical response of TiN-coated SS at low potentials is the result of electrochemical activity at the coating/electrolyte interface whereas at high potentials the increase in the current is the result of pits generated at the substrate/electrolyte interface at defects/pores within the coating.