Study of Corrosion Properties of CrN and Multilayer CrN/Cr Coating at Different Electrolyte Temperatures Deposited on Stainless Steel by Vacuum Arc Process

In our study, we have focussed on enhancing corrosion resistant properties of stainless steel grades SS304 and SS316L which are used in various chemical and fertilizer industries. Stainless steel components are utilized for processing of corrosive media at different temperatures. These components are inadequate to give protection from corrosion for long in highly corrosive media and need to be replaced frequently. To overcome this situation, chromium nitride (CrN) monolayer and multilayer CrN/Cr (M-CrN) coatings were deposited on stainless steel substrates using a state-of-the-art Advance Arc Physical Vapour Deposition process. The aqueous corrosion behaviour of the coatings was evaluated using potentiodynamic polarization method (Tafel curves) in 1.0 M HC1 solution at various temperatures i.e., 0 degrees C, 15 degrees C, 27 degrees C, 40 degrees C, 50 degrees C & 60 degrees C. The activation energy (Ea) for corrosion was calculated to understand the corrosion mechanism of the samples. The XRD analysis was carried out to identify the phase structure. Cross-sectional SEM images of the coated samples were taken to identify their growth structure and coating thickness. It was observed that the M-CrN coating on SS316L (M-CrN/SS316L) substrates show best corrosion resistance properties compared to other samples. With the increase in temperature of the electrolyte solution, the corrosion resistance properties of uncoated samples decreased. The coatings applied on the stainless steel acts as corrosion inhibitors. The Corrosion resistance and activation energy of the samples followed the order M-CrN/SS316L > MCrN/SS304 > CrN/SS316L > CrN/SS304 > SS316L > SS304. In conclusion, these coatings can be utilized in various chemical industries where components have to tackle highly corrosive medium. Hence, application of these coatings can improve the life of the components to a great extent.