Corrosion resistance of chromium nitride on low alloy steels by cathodic arc deposition

Abstract

The electrochemical behavior of deposited chromium nitride (CrN) coatings on steel has been investigated in this study. The CrN coatings were prepared by using a reactive cathodic arc plasma deposition technology in an industrial scale. The microstructure and its crystallinity of the chromium nitride have been studied using x-ray diffraction and cross-sectional transmission electron microscopy. The CrN coatings exhibit a microcolumnar morphology. The aqueous corrosion behavior of the coatings was evaluated in a saline (3% NaCl solution) environment in terms of open-circuit potentials and polarization resistance (Rp) resulting from electrochemical impedance spectroscopy. The results indicated that the CrN coatings are nobler than the uncoated steel and the Rp of the CrN coatings is at least one order of magnitude higher than that of uncoated steel. However, the Rp of the CrN coatings tend to decrease with immersion duration, showing that the corrosion changes from charge transfer to diffusion controlled, especially when the immersion time is long enough.