ELECTROCHEMICAL ANALYSIS OF CORROSION BEHAVIOR OF AL6061- SIC / GRAPHITE COMPOSITE IN VARIOUS MEDIUM

Silicon carbide particulate – reinforced Al6061 matrix alloy possess a unique combination of high specific strength, high elastic modulus, good wear resistance and good thermal stability than the corresponding nonreinforced matrix alloy system. They are used in aerospace, automobile and marine industries because of their increased corrosion resistance. In the present investigation, the corrosive behavior of Al6061-SiC particulate composites prepared by liquid metallurgy has been studied in acid chloride, acid sulphate and neutral chloride medium. Samples were prepared by taking different percentage of SiC and casted by liquid metallurgy and samples were prepared as per ASTM standard. In this paper the corrosion characteristics of as casted Al 6061/ SiC composites were experimentally assessed using Tafel extrapolation technique and A.C. Impedance or electrochemical impedance spectroscopy (EIS) technique. Polarization studies indicates an increase in corrosion resistance in composites compared to the metal matrix alloy. Tafel extrapolation technique and electrochemical impedance spectroscopy were in good agreement. It is observed that corrosion rate is more in acid chloride and acid sulphate media than in neutral chloride media. Further polarization curves indicates that corrosion rate decreases with the increase in the reinforcement content of the composite in as casted Al6061 composite. EIS study reveals that the polarization resistance (Rp) increase with increase in SiC content in composites, thus improved corrosion resistance in composites.