Corrosion resistance and surface microstructure of Mg3N2/SS thin films by plasma focus instrument

Utilizing a plasma focus (PF) instrument, magnesium nitride (Mg3N2) thin films were synthesized on stainless steel substrates. Twenty five optimum focus shots at 8 cm distance from the anode tip were used to deposit the films at different angular positions regarded to the anode axis. Scanning electron microscopy (SEM), atomic force microscopy (AFM), and X-ray diffraction (XRD) analyses were performed to assess the surface morphology and structural characteristics of Mg3N2 films. Based on AFM images, these films were studied to understand the effect of angular position variation on their surfaces through morphological and fractal parameters. By increasing the angle, we verify that the grain size decreased from 130(0) nm to 75(5) nm and also the mean quadratic surface roughness of the films reduced in its average values from (28.97 +/- 3.24) nm to (23.10 +/- 1.34) nm. Power spectrum density analysis indicated that films become more self-affine at larger angles. Furthermore, the corrosion behavior of the films was investigated through a potentiodynamic polarization test in H2SO4 solution. It was found that the ion energy and flux, varying with the angular positions from the anode tip, directly affected the nanostructured roughness and surface morphology of the samples. The electrochemical studies of films show that the uncoated sample presented the lowest corrosion resistance. The highest corrosion resistance was obtained for the sample deposited with 25 optimum shots and at 0 degrees angular position reaching a reduction in the corrosion current density of almost 800 times compared to the pure stainless steel-304 substrate.

Automated summary

Using a plasma focus instrument, Mg3N2 thin films were successfully synthesized on stainless steel substrates. The effect of angular position variation on the surface morphology and corrosion behavior of the films was investigated. The results showed that changing the angle affected the grain size, surface roughness, and corrosion resistance of the films. The sample deposited with 25 optimum shots and at 0 degrees angle exhibited the highest corrosion resistance.