Increasing the Corrosion Resistance of Austenitic Stainless Steel Products by Depositing Vanadium Nitride-Based Coatings on Their Surface

This study investigated the anticorrosive properties of nitride coatings (V,Zr,Nb)N, VN and (Zr,V)N with a thickness of approximately 3 μm, deposited on a substrate of AISI 321 steel. Experiments were conducted in 3.0 and 0.9% aqueous NaCl solutions. The results indicate that the use of (V,Zr,Nb)N, VN and (Zr,V)N coatings to protect AISI 321 steel in corrosive environments (e.g., chloride-containing solutions) allowed corrosion currents to be reduced by 10–20 times (from 7.0 to 0.29 μA/cm2) for a sample with a (Zr,V)N coating in a 3.0% aqueous NaCl solution, and by 2 times (from 0.36 to 0.18 μA/cm2) for a sample with a (V,Zr,Nb)N coating in a 0.9% aqueous NaCl solution. Based on the distribution of elements on the surface of the samples after holding for 168 h in a 3.0% aqueous NaCl solution at 25 °C, it can be qualitatively concluded that the oxidation intensity of the (Zr,V)N coating was the lowest under this condition, and that the VN coating exhibited the highest oxidation intensity among the considered coatings. Analysis of the structure of the (Zr,V)N coating after holding in a 3.0% aqueous NaCl solution for 168 h at 25 °C shows the presence of nanometre-sized chips, while the analysis of the distribution of elements does not record the presence of anything other than the elements comprising the coating. Based on the distribution of elements on the surface of the VN coating, it can be assumed that the destruction of this coating mainly occurs due to peeling off from the substrate; however, corrosion processes also occur in the VN coating itself. Analysis of the distribution of elements in the surface layers of the (V,Zr,Nb)N coating did not show noticeable signs of oxidation. The destruction of this coating occurs due to fragments peeling off from the substrate, while oxidation processes and substrate corrosion do not have a significant effect on the process of (V,Zr,Nb)N coating destruction.