TAFEL POLARIZATION AND IMPEDANCE STUDIES OF AL-7075 ALLOY AND ITS COMPOSITES IN DIFFERENT MEDIUM

Aluminum metal matrix composites because of their high potential in satisfying the recent demands have a wide variety of applications in aviation, defense system, and automobile industries. It has been noticed in research that the properties of composites can be enhanced by the addition of ceramic particles like SiC and graphite to metal matrix composites. This paper attempts on corrosion studies of Al 7075 base alloy/SiC/graphite based composites in different inorganic acid mediums (0.1M HCl,0.1M H2SO4 medium) and neutral chloride medium (3.5% NaCl medium) by making use of Tafel Polarization Technique and Electrochemical Impedance Spectroscopy Technique. Test samples were casted by taking the various percent of SiC/graphite by stir casting method as per ASTM standards. Electrochemical studies tell us about the polarization resistance and the diameter of the capacitive loops above the real axis of base alloy and composites increases in neutral chloride medium compared to different inorganic acid mediums thus it confirms that the corrosion rate in neutral chloride medium is less compared to inorganic acid mediums.Composites exhibit more resistance towards corrosion compared to Al7075 base alloy was confirmed from Ecorr and Icorr values and it was also confirmed hybrid composites are more resistant to corrosion in all the mediums.Results from Electrochemical Impedance Spectroscopy Technique and Tafel Polarization Technique were in concurrence with each other.SEM images confirm the distribution of reinforcement particulates in the metal matrix and let out the rate of degradation of alloy and composites in different mediums.