Corrosion Behavior of Coatings of Titanium Nitride and Titanium-Titanium Nitride on Steel Substrates

It is well known that titanium nitride (TiN) coatings produced by physical vapor deposition (PVD) have a limited corrosion resistance, as a result of their intrinsic porosity. Some attempts have been made to improve corrosion resistance, by such measures as increasing film thickness. The deposition of Ti inter-layers are known to improve not only corrosion resistance but also adherence, probably because the oxygen present forms a passive film of titanium dioxide (TiO₂) and promotes a partial closing of defects. This would allow the use of thin films of TiN, maintaining the quality of the protection without a rise in costs associated with greater thicknesses. In the present work conventional electrochemical assays were performed. Results were compared with previous studies made on substrates without Ti interlayers. The addition of an intermediate layer is a standard technical coating process aimed at improving adhesion. Nonetheless, the comparison of a Ti + TiN coating with a pure TiN film was useful to understand the mechanisms involved in their corrosion behavior.