Search

Corrosion behavior of diamond-like carbon (DLC) films was evaluated via potentiodynamic polarization in a 3.5 wt. % NaCl solution with pH 2 at room temperature. The polarization results elucidated that the corrosion resistance of the films was enhanced with the variation of the chemical compositions and film thicknesses. The use of the spectromicroscopy method in the investigation of the pitting corrosion was a success in this study. Formation of orbital mapping, bonding state, and composition of the DLC films at non-corrosion and corrosion areas indicate the different structures between DLC and graphite oxide. Also, the π* (C=C) and π* (C=O) bonding states were found to increase in the corrosion areas. This finding not only exhibited the increase of sp² content but also promoted the rise of oxygen atoms in corrosion zones. Consequently, the present results indicate that the synchrotron--based spectromicroscopy plays an important role in the characterization of the corrosion on DLC films. [ABSTRACT FROM AUTHOR]

Chromium nitride film (CrN) was prepared on steel substrates, AISI 4140 and H13 with variations in the substrate roughness, using the reactive DC magnetron sputtering technique at room temperature in controlled partial pressures of Ar and N2 gas atmospheres. The films were polycrystalline, as confirmed by X-ray diffraction analysis. The corrosion behavior was investigated using an electrochemical technique in 3.5 wt% NaCl solution with various pH values at room temperature. The results indicated that the CrN-coated AISI H13 presents better corrosion resistance than the CrN-coated AISI 4140 at pH 2 and 7, but worse at pH 10. In addition, the rate of corrosion decreased with a reduction of the surface roughness. The chemical states of the corrosion product were clearly identified by spatially resolved secondary electron yield X-ray absorption spectroscopy with X-ray photoemission electron microscopy. It was found that Cr2O3 is formed on the non-corroded CrN film and the AISI H13 substrate, whereas Fe2O3 is formed on the corroded surface and the AISI 4140 substrate. [ABSTRACT FROM AUTHOR]