Degradation of aluminum metal matrix composites in salt water and its control

Alloy Al 6013-20 Si in tempers O, F and T4 showed good resistance to corrosion in salt spray tests. The corrosion rate of the alloy decreased with increased exposure time due to the formation of boehmite (AlO·OH). Studies conducted in 3.5 wt.% NaCl solution containing suspended particles of polystyrene showed a linear increase in the erosion–corrosion rate with velocity. The localized attack was concentrated mainly on the Al 6013/SiC interface. A high dislocation density was observed at the Al 6013/SiC interface, which interfered with the formation of a homogeneous protective film of boehmite on the alloy surface. Addition of cerium chloride drastically suppressed the rate of corrosion. Sodium molybdate offered a lesser degree of protection compared to cerium chloride.