Corrosion resistance of CrN PVD coatings: comparison among different deposition techniques

Corrosion resistance of CrN PVD coatings were evaluated with polarization tests in NaCl and HCl environment. The effect of the deposition technique and the related defects morphology were studied and corrosion mechanisms were evaluated on the basis of the detected defects type. It was found that the presence of two layers in coating architecture delays corrosion; this solution is a good advice in designing coatings for applications where good corrosion resistance is required. Coating porosity, calculated using two different models available in literature, was compared with experimental evidences. Formulas based on polarization resistance are in agreement with morphological SEM analyses but, on the contrary, mixed potential model appears not suitable for coating porosity calculation.