Effect of cermet interlayer on the electrochemical behavior of Cr3C2-NiCr/DLC duplex coating.

Duplex coating consisting of a Cr 3 C 2 -NiCr interlayer and a top DLC film was prepared using the high-velocity oxyfuel (HVOF) spraying and a closed field unbalanced magnetron sputtering (CFUBMS). The electrochemical behaviors of the Cr 3 C 2 -NiCr/DLC duplex coatings in 3.5 wt% NaCl solution was investigated by comparing it with a single DLC film and a single Cr 3 C 2 -NiCr coating. Then the role of cermet interlayer on the anticorrosion mechanism of the duplex coatings was explored. Results showed that introducing the cermet interlayer increased the surface roughness of DLC films without changing its microstructure. In the dynamic potential polarization test, duplex coatings maintained high surface integrity even after corrosion, and corrosion only occurs in localized areas. The inclusion of an interlayer avoided substrate corrosion caused by penetrating cracks and therefore provided excellent corrosion resistance. • The top DLC film covers the pores of the Cr 3 C 2 -NiCr coating. • The corrosion occurs the island boundaries, but duplex coating remains dense surface. • Oxide of Cr and Ni protects the coating system from diffusion of corrosive ions. [ABSTRACT FROM AUTHOR]