Corrosion protection of 304 stainless steel bipolar plates using TiC films produced by high-energy micro-arc alloying process

Metallic bipolar plates look promising for the replacement of graphite due to higher mechanical strength, better durability to shocks and vibration, no gas permeability, acceptable material cost and superior applicability to mass production. However, the corrosion and passivation of metals in environments of proton exchange membrane fuel cell (PEMFC) cause considerable power degradation. Great attempts were conducted to improve the corrosion resistance of metals while keeping low contact resistance. In this paper, a simple, novel and cost-effective high-energy micro-arc alloying process was employed to prepare compact titanium carbide as coatings for the type 304 stainless steel bipolar plates with a metallurgical bonding between the coating and substrate. It was found that TiC coating increased the corrosion potential of the bare steel in 1 M H₂SO₄ solution at room temperature by more than 200 mV, and decreased significantly its corrosion current density from 8.3 μA cm⁻² for the bare steel to 0.034 μA cm⁻² for the TiC-coated steel. No obvious degradation was observed for the TiC coatings after 30-day exposure in solution.