Temperature-induced anodic dissolution and degradation of through-plane conductivity in C/Ti coated metal bipolar plates

The temperature-dependent corrosion behaviour and through-plane conductivity of nano-thin carbon/titanium/stainless steel (C/Ti/SS316L) composite coatings in a DOE-specified simulated PEMFC cathode environment (0.1 ppm HF, pH 3) were investigated. Elevated temperatures accelerated mass transfer, reducing corrosion resistance via negative corrosion potential shifts, increased corrosion current density, and lower impedance modulus. Under 0.67 V polarisation, coatings maintained low corrosion current density (<0.5 μA cm −2 ) and ICR (<2 mΩ cm 2 ) even at 90°C, meeting DOE targets. Conversely, polarisation at 1.43 V and high temperatures triggered preferential carbon corrosion, Ti interlayer exposure/dissolution, and Ti-oxide formation/dissolution, degrading through-plane conductivity. A temperature-dependent anodic dissolution transition is proposed: Ti-interlayer-controlled dissolution at moderate temperatures shifts to synergistic Ti dissolution and carbon corrosion at high temperatures. These findings define a safe operating temperature window for C/Ti-coated bipolar plates, supporting their practical PEMFC applications.