Hydrothermal oxidation of titanium nitride coating for enhanced corrosion resistance in fluoride-containing acidic solution

To improve the corrosion resistance of titanium nitride (TiN) coating in acidic solution containing fluoride ions (F-), surface hydrothermal oxidation was conducted. Pure water was used as the medium and at temperatures as low as 200-250 degrees C, a thin, uniform and dense titanium oxide (TiO2) nanolayer composed of well-crystallized anatase nanoparticles was fabricated. The TiO2 layer was grown in situ, and its (004) planes aligned well with the (1 1 1) planes of underlying TiN; the transition zone was only a few atomic layers thick. Hydrothermal oxidation improved the chemical stability and decreased the corrosion rate of TiN coating in 0.5 mol/L sulfuric acid solution containing 0.05 wt% F-. When fabricated at 250 degrees C, the TiO2 layer remained intact after immersion test, providing good protection for the underlying TiN.