Deposition of diamond-like carbon films on the inner surface of narrow stainless steel tubes

Diamond-like carbon (DLC) films were deposited on the inner surface of 304-type stainless steel tube with an inner diameter of 10 mm by DC glow discharge plasma. The influence of the deposition time, pressure and the ratios of CH4 in CH4/Ar gas mixture on the DLC film deposition were investigated. The images of Scanning Electron Microscopy (SEM) show that the DLC films are featureless and free of porosity. Fibre-like structure was recognized on the film surface by Atomic Force Microscopy (AFM). The film deposition rate decreases with increasing the deposition time. Relative higher deposition rate (40 nm/min) can be obtained at 20-30 Pa, higher and lower pressure will significantly decrease the deposition rate. Raman spectrum analysis shows that the films deposited in 30 min at 20-30 Pa have more sp3 content. The corrosion resistance of the films was measured by potentiodynamic polarization test. The DLC films deposited on the inner surface of the 304-type stainless steel tube significantly improve its corrosion resistance.