Effect of C/Si ratio on the electrochemical behavior of a-SiCx:H coatings on SS301 substrate deposited by PECVD

Amorphous hydrogenated silicon carbide (a-SiCx:H) coatings were deposited on stainless steel 301 (SS301) using plasma enhanced chemical vapor deposition with the methane gas flow ranging from 30 to 90 sccm. XRD spectra confirmed the amorphous structure of these coatings. The as-deposited coatings all exhibited homogenous dense feature, and no porosities were observed in SEM and AFM analysis. The a-SiCx:H coatings remarkably increased the corrosion resistance of the SS301 substrate. With the increase of the C concentration, the a-SiCx:H coatings exhibited significantly enhanced electrochemical behavior. The a-SiCx:H coating with the highest carbon concentration acted as an excellent barrier to charge transfer, with a corrosion current of 3.5 × 10−12 A/cm2 and a breakdown voltage of 1.36 V, compared to 2.5 × 10−8 A/cm2 and 0.34 V for the SS301 substrate.