Electrodeposition of Diamond-like Carbon (DLC) Films on Mg by Plasma Electrolysis

Diamond-like carbon (DLC) films were deposited on Mg substrate in CH3OH and KNO3 solution by the liquid-phase electrodeposition technique at ambient pressure and temperature. The applied voltage between the electrodes was low (130 V) due to the use of conductive inorganic liquids. The surface morphology was examined by Scanning Electron Microscopy (SEM). Corrosion performance of the films was investigated by potentiodynamic polararization tests and electrochemical impedance spectroscopy (EIS) in 3.5% NaCI solution. The structure of the films was characterized by X-ray photoelectron spectroscopy (XPS) and Raman spectroscopy. Raman spectroscopy analysis of the films revealed two broad bands at approximately 1369.5 and 1554.7 cm(-1), relating to D and G-band of typical DLC film, respectively. The low intensity ratio of I-D/I-G indicate that the DLC films have a high ratio of sp(3) to sp(2) bonding, which is also in accordance with the results of XPS spectra. SEM showed that DLC film was uniform, homogeneous but rough. Potentiodynamic polarization curve and EIS indicated the corrosion resistance of the Mg substrate was markedly improved by DLC films. A mechanism for the formation of sp(3) and sp(2) hybridizations is proposed. (C) The Electrochemical Society of Japan, All rights reserved.