Long-term corrosion study of low carbon steel coated with titanium boronitride in simulated soil solution

A new type of titanium boronitride (TiBN) coating was prepared by chemical vapor deposition (CVD) on low carbon steel (LCS). The coating morphology, chemical composition and crystal structure were studied by different characterization techniques, before and after corrosion testing. Corrosion testing was carried out by electrochemical techniques (open-circuit potential, polarization curves, impedance spectroscopy) in simulated soil solution. The TiBN coating provides an excellent corrosion protection for the steel substrate, up to the tested 90 days of immersion. Even though minor changes in the coating composition and phase structure were observed after long-term immersion, this does not decrease the protective nature of the coating. An analysis of the impedance data indicates that the coating may initially contain very small defects (pinholes), which gradually are blocked by corrosion products, improving the corrosion resistivity of the coated steel. (C) 2012 Elsevier Ltd. All rights reserved.