Corrosion resistance of nano-sized SiC-rich composite coatings produced by noble gas ion mixing.

Ion beam mixing has been used to produce silicon carbide (SiC) rich nano layer for protective coating. Different C/Si/C/Si/C/Si(substrate) multilayer structures (with individual layer thicknesses falling in the range of 10-20nm) have been irradiated by Ar+ and Xe+ ions at room temperature in the energy and fluence ranges of 40-120 keV and 1-6x1016 ion/cm2, respectively. The effects of ion irradiation including the in-depth distribution of the SiC produced was determined by Auger electron spectroscopy depth profiling. The thickness of the SiC-rich region was only some nanometers and it could be tailored by changing the layer structure and the ion irradiation conditions. The corrosion resistance of the layers was investigated by potentiodynamic electrochemical test in 4M KOH solution. The measured corrosion resistance of the SiC-rich layers was orders of magnitude better than that of pure silicon and a correlation was found between the corrosion current density and the effective areal density of the SiC.