Research About Electrochemical Corrosion Behavior Of NiTi Archwires Coated With Diamond-like Carbon

Objective:To evaluate and compare the corrosion resistance of diamond-like carbon coated nickel-titanium arch wires( DLC-Ni Ti) and uncoated nickel-titanium arch wires( Ni Ti) in different artificial saliva with different fluoride( F-)and PH.Methods:Diamond-like carbon( DLC) coatings were prepared by radiofrequency magnetron sputtering technique on nickel-titanium arch wires.Raman spectrum was used for characterization. DLC-Ni Ti wires were taken as experimental group, and Ni Ti wires as control group, and both were exposed to four kinds of artificial saliva(A: PH=7; B:PH =7, 0.2%F-; C:PH =7, 0.5% F-; D:PH =5, 0.5% F-). Potentiodynamic polarization curves(Tafel curves)of DLC-Ni Ti and Ni Ti wires were measured via the classic three electrode system of electrochemical workstation. Then,the corrosion potential( Ecorr) which represents corrosion tendency and the corrosion current density( Icorr) which represents corrosion rate were acquired, and scanning electron microscope( SEM) was used for morphological observation before and after corrosion.Results:1. Raman spectra from surface of DLC-Ni Ti wires showed typical D peak and G peak,indicating that Ni Ti wires had been coated by DLC.2. With the fluoride concentration increasing and PH declining,the corrosion tendency and the corrosion rate of Ni Ti and DLC-Ni Ti wires also increased after corrosion in the artificial saliva(P<0.05).3. After corrosion in the same group of artificial saliva, the corrosion tendency and the corrosion rate of DLC-Ni Ti was apparently lower than Ni Ti(P<0.05).4. The Tafel curves of Ni Ti and DLC-Ni Ti moved to the left with the fluoride concentration increasing and the PH declining,which indicated worse corrosion resistance.5. Under the scanning electron microscope, much pitting corrosion was observable on the surface of Ni Ti wires while few was on the surface of DLC-Ni Ti wires.Conclusion:1. Diamond-like carbon coatings have been successfully prepared by radio-frequency magnetron sputtering technique on nickel-titanium arch wires at a low temperature.2. The fluoride concentration and the PH have side effects on the corrosion resistance of Ni Ti and DLC-Ni Ti wires.3. The corrosion resistance of DLC-Ni Ti wires is better than that of Ni Ti wires,that is to say DLC coatings help to prevent Ni Ti wires from electrochemical corrosion in saliva.