Comparison between corrosion behaviour of DLC and N-DLC coatings deposited by DC-pulsed PACVD technique

DC-pulsed PACVD technique was employed for deposition of nitrogen-doped DLC and DLC coatings on 316 stainless steel. The Raman spectroscopy and AFM analysis were utilized to evaluate the structural properties and surface morphology of the coatings. In order to investigate the wettability of the samples, surface energy was calculated using optical contact angle. Potentiodynamic polarization and EIS tests were applied to assess the corrosion behaviour of the specimens. Moreover, XPS investigation was undertaken in order to study corrosion mechanism of the coatings after immersion in 3.5 wt% NaCl solution for one week. It was found that the DLC coating has better corrosion resistance compared to N-DLC coating. Furthermore, higher reduction of CC (sp2) bonds compared to CC (sp3) bonds was observed after the immersion test. Additionally, the amount of CO and COOH bonds in DLC coatings increased more than N-DLC coating.