Effect of Si addition to CrN coatings on the corrosion resistance of CrN/stainless steel coating/substrate system in a deaerated 3.5 wt.% NaCl solution

CrSiN coatings with different Si concentration (Si/(Cr + Si) ratio: 0, 3.7, 11.7, 20%) were deposited on stainless steel substrates using a closed field unbalanced magnetron sputtering (CFUBM) system. The variation in the microstructure of the films with the Si concentration was measured by XRD. The corrosion behavior of the CrSiN coatings in a deaerated 3.5% NaCl solution was investigated by potentiodynamic tests, electrochemical impedance spectroscopy (EIS) and surface analyses. The microstructure of the CrSiN film was found to depend on the Si concentration. The results of the potentiodynamic polarization tests showed that the corrosion current density and porosity decreased with increasing Si/(Cr + Si) ratio. The EIS measurements showed that the corrosion resistance of the Si-bearing CrN was improved by the phase transformation of the film, which led to an increase in the pore resistance and charge transfer resistance. The Si-bearing CrN possesses the best corrosion resistance at a Si/(Cr + Si) ratio of 20%, measured by the maximization of the pore resistance and charge transfer resistance.