Corrosion behavior of SiC p /6061 Al metal matrix composites in chloride solutions

The corrosion behavior of silicon carbide particulates-aluminum metal matrix composites was studied in chloride solution by means of electrochemical techniques, scanning electron microscope (SEM), transmission electron microscope (TEM) and optical microscope. The materials under investigation were compocasting processed 6061 Al reinforced with increasing amounts of SiC particulates. Electrochemical tests such as potentiostatic polarization were done in 0.1 kmol·m^–3 NaCl solutions that were aerated and deaerated to observe overall corrosion behavior. In addition, pit morphology was observed after immersion tests. It was seen that the pitting potentials did not vary greatly or show definite trends in relation to the amounts of SiC_p reinforcement. However, the degree of corrosion increased with increasing SiC_p content; probably mainly due to galvanic couple. No intermetallics layer was found at the SiC_p/Al interface. Based on pitting potentials of Al-Si alloys, a pitting process around SiC particulate was proposed.Abbreviations SiC_p (silicon carbide particulates) - SiC_f (silicon carbide fibers) - SiC_w (silicon carbide whiskers) - E_pit (pitting potential) - E_prot (protection potential) - E_corr (corrosion potential) - i_galv (galvanic current density) - E_galv (galvanic potential)