Chemical vapor deposition of titanium based ceramic coatings on low carbon steel: Characterization and electrochemical evaluation

Titanium nitride (TiN), titanium boride (TiB2) and titanium boronitride (TiBN) with different boron content were deposited on low carbon steel by Chemical Vapor Deposition (CVD) technique. The CVD was performed at a temperature of 900 °C and a reduced pressure of 600 mbar. To elucidate the corrosion protection mechanisms of the coatings, their chemical composition was studied by XPS, the morphology by SEM and the crystallographic structure by XRD. The corrosion behavior was evaluated in simulated soil solution (SSS) by potentiodynamic polarization curves and electrochemical impedance spectroscopy (EIS). The EIS experimental data were analyzed by an equivalent circuit model. The results demonstrate that titanium boronitride coatings provide excellent corrosion protection to the low carbon steel, which is related to the high chemical stability as well as to their favorable microstructure.