Phase orientation improved the corrosion resistance and conductivity of Cr2AlC coatings for metal bipolar plates

Abstract

In view of the Mn+1AXn (MAX) phase coatings benefiting the adaptive passivation film for good corrosion resistance and high electronic density of states for excellent electrical conductivity, here, we reported the Cr2AlC MAX phase coatings with different preferred orientations by a homemade technique consisting of vacuum arc and magnetron sputtering. The dependence of surface and interface microstructural evolution upon the corrosion and electrochemical properties of deposited coating was focused. Results showed that all the Cr2AlC coatings with different phase orientations greatly improved the performance of stainless steel (SS) 316 L substrate. Specifically, the lowest value of interface contact resistance (ICR) reached to 3.16 mΩ cm2 and the lowest corrosion current density was 2 × 10−2 μA cm−2, which were much better than those of bare SS316L. The combined studies of electrochemical properties and theoretical calculations demonstrated that the Cr2AlC coatings with preferred (103) orientation were easier to form oxide passivation film on their surface to increase the corrosion resistance.