Electrochemical properties and surface conductivity of Ti-Al coating on Ti-6Al-4V

Ti-Al compound coatings with both metallic and ceramic properties are prepared on the surface of Ti-6Al-4V(TC4) by simple heat treatment, making it a promising modification method for the titanium bipolar plate, a core component in proton exchange membrane fuel cell (PEMFC). The effects of heat treatment on the formation mechanism, microstructure, corrosion resistance, interface contact resistance (ICR), and water contact angle of the coatings are systematically investigated. The Ti3Al phase and TiAl phase co-exist on the surface of the heat-treated samples at 900 °C and above. The corrosion resistance of the coating is evaluated in a simulated PEMFC environment and an accelerated corrosion environment. The coated sample prepared at 950 °C presents the lowest corrosion current density, followed by the coated sample prepared at 900 °C (PC-900). The ICR value of PC-900 (4.9 mΩ·cm2) is comparable to that of a graphite plate. The water contact angles of all coated samples are higher than that of TC4 alloy and it reaches 111.22° for PC-900, exhibiting a good hydrophobicity. All the above results indicate the PC-900 satisfies the standard from the US Department of Energy.