Surface characteristics and electrochemical corrosion behavior of NiTi coated with diamond-like carbon

Diamond-like carbon (DLC) films were produced on NiTi substrate by plasma immersion ion implantation and deposition (PIIID) at room temperature. Surface morphology and roughness were analyzed by atomic force microscopy. Film microstructure and hardness were characterized by Raman scattering spectroscopy and nano-indentation, respectively. The corrosion resistance in Hankʹs solution was evaluated by means of open-circuit potential (OCP) and potentiodynamic polarization techniques. It was found that, according to the corrosion potential (EOCP), the coated sample is always more noble than the uncoated one. For the polarization curves, the shift of the breakdown potential to more positive values and the reduction of the current densities give evidence that the coating with DLC is a useful method for reducing the corrosion attack of the NiTi alloy in Hankʹs solution.