Effect of vacuum heat treatment temperature on anti-corrosion and conductivity properties of C/TiC nanocomposite coated titanium foil for PEMFC bipolar plates

Abstract

In this work, a C/TiC nanocomposite coating was prepared on titanium foil using a combination of magnetron sputtering and heat treatment technology to improve the corrosion resistance and conductivity of bipolar plates. The effect of heat treatment temperature on surface morphology, chemical composition, mechanical property, hydrophobicity, corrosion resistance and conductivity of coated samples was investigated. The results indicate that the roughness of the coating increase with heat-treated temperature and the corrosion current density (icorr) firstly decreases and then increases in 0.5 M H2SO4 solution containing 5 ppm HF at 80 ℃, reducing its smallest value at 700 ℃ (1.28 μA cm−2), which is declined by 3 orders of magnitude compared to the substrate (562.90 μA cm−2). After potentiostatic polarization experiment (PP) for 12 h, the polarization current density (ipp) of the coatings firstly reduces and then increases, with values of 1.48, 0.70, 0.36, 0.41, 1.32 and 1.35 μA cm−2 corresponding to the substrate and coated samples, respectively. Furthermore, the interface contact resistance (ICR) of coated samples firstly decreases and then increase with temperature rising, which are less than 10 mΩ cm2. After 12 h PP tests, the ICR increase, with values of 18.42, 26.28, 13.64, 10.26 and 11.56 mΩ cm2 corresponding to RT, 600 700 800 and 900 ℃, respectively. The water contact angle of the coated sample for 600 and 700 ℃ are higher than that of other samples and they reached 87.6°and 85.3°, exhibiting a good hydrophobicity.