Corrosion Behavior of SiCp/6061 Al Metal Matrix Composites

The corrosion behavior of silicon carbide/aluminum (SiCp/Al) metal matrix composites was studied in chloride solution by means of electrochemical techniques, scanning electron microscopy (SEM), Auger electron spectroscopy (AES), energy dispersive spectroscopy (EDS), and X-ray diffraction. The materials under investigation were powder metallurgy (P/M) processed 6061 Al reinforced with increasing amounts of SiC particles (15 to 40 vol%). Electrochemical tests such as potentiodynamic polarization were done in 0.035, 0.35, and 3.5% NaCl solutions that were open to air, aerated, or deaerated to observe overall corrosion behavior. In addition, pit morphology was observed after anodic polarization to a number of potentials. It was seen that the corrosion potentials did not vary greatly or show definite trends in relation to the amounts of SiCp reinforcement. However, the degree of corrosion increased with increasing SiCp content and the presence or absence of oxygen as well as the concentration of the NaCl solution did affect corrosion potentials. Microscopic analysis techniques were used to study the corroded samples and the extensive pitting and exfoliation of the surfaces. X-ray diffraction was used to identify the compounds on the surface of the corroded samples as well as the flakes due to exfoliation.