Improved corrosion resistance of cathodic arc evaporated Al₀.₇Cr₀.₃−ₓVₓN coatings in NaCl-rich media

Abstract

The corrosion resistance of cathodic arc evaporated Al₀.₇Cr₀.₃−ₓVₓN coatings with a vanadium content up to 22.3 at% has been electrochemically tested in a 0.1 M NaCl-solution. Significant improvement in the open porosity and corrosion rate was observed for coatings with higher V-contents, due to a denser and more refined coating morphology. Further reduction in the open porosity rate was achieved through an annealing step in air at 700 °C. Here, the formation of an AlVO₄ top-oxide and underlying oxygen-rich V-depletion zone provides additional sealing of the coating surface, whilst reducing the corrosion current density to a final 1.59 × 10−9 A/cm2.