Investigation of wear and corrosion characteristics of PTFE/TiN composite coating on SS-304 fabricated by two-step sputtering technique

Abstract

Polytetrafluoroethylene (PTFE) and titanium nitride (TiN) composite coatings have proved to be quite effective anti-corrosion applications owing to the inertness of PTFE and wear resistance of TiN. However, there has been a significant research gap due to the lack of detailed investigation into the mechanisms and characterizations. Inspired by this, our work is focused on investigating the in-depth electrochemical corrosion characteristics of PTFE/TiN composite coating while exploring the contact angles and wear-resistant mechanisms. The PTFE/TiN composite was directly coated on stainless steel (SS-304) substrate by RF magnetron sputtering in two steps. The experimental results indicated that the coating of the PTFE layer modified the characteristic hydrophilic character (θw ~ 78.2° ± 2°) of the SS-304 surface into an almost superhydrophobic character (θw ~ 142.6° ± 2°), indorsing the superior protection of SS-304 from aqueous species. Our electrochemical studies revealed that after long-time immersion (6 h) in an alkaline medium, our coating demonstrated a corrosion rate as slow as 0.0026 μm/year with a low surface energy of 4.81 mN/m and high hardness of 16.78 ± 0.36 GPa. Besides, the maximum wear resistance and maximum resistance to fatigue fracture ratios were obtained as H/Er ~ 0.064 and H3/E 2– 0.068 GPa, respectively. Furthermore, the coating also displayed excellent durability when exposed to air and immersion in chloride solution for a longer time. Lastly, we have included an in-depth discussion of the process steps as well as the mechanism of corrosion initiation.