Effect of annealing on microstructure evolution and corrosion resistance of an amorphous Cr-Al-C coating

Abstract The microstructure evolution of an amorphous Cr-Al-C coating prepared by magnetron sputtering was investigated. With increasing annealing temperature, three kinds of coatings, including amorphous coating, partially crystallized coating ((Cr,Al)2Cx solid solution), and fully crystallized coating (Cr2AlC MAX phase), were obtained. The electrochemical measurements in 3.5 wt. % NaCl solutions indicated that all of the coatings exhibited passivation behaviors, and amorphous coating possessed the lowest passive current density. All the passive films exhibited p-type semiconductor characteristics, and the passive film on amorphous coating provided the best protection due to the presence of a relatively high content of Cr2O3.