The passivity and protective nature of the passive films are essentially related to ionic and electronic transport processes, which are controlled by the optical and electronic properties of passive films. In this study, the electrochemical behavior of passive films anodically formed on AISI 304 stainless steel in sulfuric acid solution has been examined using electrochemical impedance spectroscopy. AISI 304 in sulphuric acid solution is characterized by high interfacial impedance, thereby illustrating its high corrosion resistance. Results showed that the interfacial impedance and the polarization resistance () initially increase with applied potential, within the low potential passive. However, at a sufficiently high potential passive ( V), the interfacial impedance and the polarization resistance decrease with increasing potential. An electrical equivalent circuit based on the impedance analysis, which describes the behavior of the passive film on stainless steel more satisfactorily than the proposed models, is presented.

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In this study, a zirconium nitride/chromium nitride nano-multilayer coating was deposited on AISI 304 specimen using cathodic arc evaporation-physical vapor deposition (CAE-PVD). The characterization of the samples were evaluated by scanning electron microscopy (SEM), field emission-SEM (FE-SEM), and X-ray diffraction (XRD). To evaluate effect of immersion time on the electrochemical behavior of ZrN/CrN nano-multilayer coating using electrochemical impedance spectroscopy (EIS) measurements were carried out in 3.5 wt. % NaCl media. Using the CAE-PVD method, nano-multilayer ZrN/CrN coating with high adhesion and density was successfully produced. A unique high polarization resistance of ZrN/CrN nano-multilayer coatings in comparison to AISI 304 stainless steel without coating was made. As well as the desirable behavior corrosion results showed that in the ZrN/CrN nano-multilayer coating to the AISI 304 substrate within the 3.5 wt. % NaCl, there is a barrier against corrosive agents that is preventing corrosion occurrence. The SEM images disclosed that there were not any pits or severe damages on the surface of the ZrN/CrN nano-multilayer coating. The FE-SEM micrographs show that the coating structure contains alternate layers of ZrN and CrN. The energy dispersive spectroscopy (EDS) analysis and x-ray map were disclosed elements distribution in the cross-section of the nano-multilayer coating.

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