Corrosion Behaviour of Heat - Treated Al-6063/ SiCp Composites Immersed in 5 wt% NaCl Solution

The influence of SiC volume percent and temper conditions (namely, as-cast, solutionized, and artificial age hardening at 180°C and 195°C) on the corrosion behaviour of Al (6063) composites and its monolithic alloy immersed in 5wt% NaCl solution has been investigated. Al (6063) - SiC particulate composites containing 6, 12 and 15 volume percent SiC were produced by premixing the SiC particles with borax additive and then adopting two step stir casting. Mass loss and corrosion rate measurements were utilized as criteria for evaluating the corrosion behaviour of the composites. The results show that the corrosion susceptibility of the Al (6063) - SiCp composites was higher than that of the monolithic alloy, and for most cases the corrosion rate of the composites increased with increase in volume percent of SiC. However, it was discovered that the nature of the passive films formed on the composites was sufficiently stable to reduce significantly the corrosion rate of the composites after 13days of immersion. This trend was observed to be consistent for all heat-treatment conditions utilized.