Surface characteristics and electrochemical corrosion behavior of fluorinated diamond-like carbon (F-DLC) films on the NiTi alloys

Fluorinated diamond-like carbon (F-DLC) films with different CF4 flux were deposited on polished NiTi alloys by plasma immersion ion implantation and deposition (PIIID). The results show CFx bond is formed in the F-DLC films. With the increase of the CF4 flux, the fluorine content and surface hydrophilicity of the F-DLC films are increased, while their sp3/sp2 ratio and surface roughness are decreased. The F-DLC films improve the surface corrosion resistance of NiTi alloys, and the corrosion resistance of the F-DLC films on the NiTi alloys first increase and then decrease with increasing the CF4 flux. Moreover, the relationship between the corrosion resistance and its structure and surface hydrophilicity of the F-DLC films is also clarified.