Balancing the corrosion resistance and conductivity of Cr-Al-C coatings via annealing treatment for metal bipolar plates.

[Display omitted] • The Cr-Al-C coatings with different crystallization states were manipulated here. • The partially crystallized Cr-Al-C coatings exhibited the best performance. • Mechanism of conductive corrosion resistance was clarified by HAADF and EPR. • Partially crystallized Cr-Al-C coatings were promising candidate in BPs protection. Metal bipolar plates (BPs) with excellent corrosion resistance and good conductivity have been becoming one of key issues to explore proton exchange membrane fuel cells (PEMFCs). Here, we fabricated the high-performance protective Cr-Al-C coatings on stainless steel 316L using a combined cathodic arc and magnetron sputtering deposition with subsequent annealing. The electrochemical measurements in 0.5 M H 2 SO 4 + 5 ppm HF solution and interfacial contact resistance (ICR) tests indicated that all the coatings exhibited enhanced corrosion resistance and excellent conductivity. As the annealing time increased, enhanced conductivity and corrosion current density were observed. Particularly, the sample annealed at 550 °C for 2 h exhibited the best comprehensive performance in balancing the corrosion current density of 3.02 × 10-7A cm−2 and ICR of 4.5 mΩ cm2 under 140 N cm−2, respectively. The present work provides the alternative strategy to apply the promising Cr-Al-C coatings for high-performance metal BPs used in PEMFCs. [ABSTRACT FROM AUTHOR]