We have studied the corrosion behavior of CrN coatings, obtained by unbalanced magnetron sputtering (UBM) on substrates of AISI 304 and ASTM A36, using the electrochemical impedance spectroscopy technique (EIS) in electrolyte of NaCl 3% wt. In order to determine the mechanisms of protection and failure of these systems, we correlated the polarization resistance (Rp) in time function, with the morphology and chemical composition. To do this, we characterized the microstructure of the coatings by scanning electron microscopy (SEM), the crystalline phases with X-ray diffraction (XRD) and chemical composition, before and after exposure to a corrosive environment, by X-ray photoelectron spectroscopy (XPS) and Auger electrons (AES). In general, the corrosion resistance of CrN coatings is totally influenced by the substrate. The best corrosion resistance was achieved in the film deposited on stainless steel, than was observed with the increased in the polarization resistance. These details are discussed in this research.