Mechanism of localized corrosion of aluminum-silicon carbide composites in a chloride containing environment

In marine environments, more pits develop on SiC reinforced aluminum alloy composites than on their unreinforced counterparts. Although it has been suggested that the SiC plays an active role in composite corrosion by fostering the initiation of pits, this fact has not been conclusively demonstrated. The present paper considers data of two independent investigations concerning the effects of alloy type, and heat treatment on pit initiation in SiC reinforced aluminum composites. For four alloys, it is shown that pit initiation is dependent on the alloy type and heat treatment. Further, microscopic observations show that pit initiation sites are correlated with secondary phase particles. Results suggest that secondary phases/rather than the SiC particles, contribute to the pitting behavior of the composites.