Evaluation of corrosion resistance in saline environment of ZrN and ZrSiN coatings deposited on 304L stainless steel by reactive magnetron sputtering

Coated materials have been applied in different situations. The aim of this research is to study the deposition process, by reactive magnetron sputtering, of ZrN and ZrSiN coatings containing different silicon ratio, Si/(Zr+Si)%, their characterization and corrosion resistance evaluation of deposited films on 304L stainless steel in a saline medium. Firstly, deposition process occurred and all parameters were fixed, except the Si target power, which varied from 35 W to 80 W. Later, electrochemical impedance spectroscopy (EIS) and potentiodynamic polarization tests were conducted, both after one-hour immersion, measuring open potential circuit (OCP) in 3.5% (w/v) NaCl solution. Samples characterization was developed using X ray diffraction (XRD), atomic force microscopy (AFM) and scanning electron microscopy/ energy dispersive spectroscopy (SEM/EDS). As result, XRD patterns presented (111) crystallography preferential plane, with a broadening and slight low peak intensity on high silicon concentration samples. Thickness and roughness measurements were obtained by AFM technique, verifying the proportional correlation between these parameters, while SEM/EDS analysis proved that films were homogeneous and uniformly deposited. Analyzing potentiodynamic polarization results was possible to conclude that all films enhanced the corrosion resistance because of lower passivation current density values than uncoated 304L (acting as protective barrier), but presenting similar breakdown potential values. By EIS technique results, coated samples presented higher polarization resistance than uncoated 304L, and ZrN films obtained the highest Rpo and Rct values. As conclusion, coatings increased the corrosion resistance of 304L stainless steel in a saline medium, while ZrN showed the best performance. (author)