Corrosion resistance and conductivity behavior of Cr-Al-N MAX phase coatings prepared by magnetron sputtering technology

Chromium aluminum nitride (CrAlN) coatings containing Cr₂AlN phase were prepared by unbalanced magnetron sputtering followed by annealing at 1000 °C. The crystal structures, X-ray diffraction patterns, and selected area electron diffraction patterns of the Cr₂AlN phase were modeled using computer software and compared with experimental observations. A good agreement was found between the two sets of results, thereby confirming the presence of Cr₂AlN phase in the coatings. While previous studies have demonstrated the formation of Cr₂AlN phase theoretically, this study presents experimental evidence of its physical existence. The potentiodynamic polarization results and interfacial contact resistance measurements show that the CrAlN coating with Cr₂AlN phase has excellent corrosion resistance (a corrosion current density of 5.35 × 10⁻⁷ A/cm² and electrical conductivity of 5.5 mΩ·cm²) and is thus a promising candidate for the protection of fuel cell bipolar plates.