Influence of SiCp content and matrix composition on corrosion resistance in cast aluminium matrix composites in salt fog

A study has been carried out into the influence of the proportion of SiCp and the matrix composition of four aluminium metal matrix composites (A360/SWCl10p, A360lSiCl20p, A380/SiCl 10p and A380/SiCl20p) on their salt corrosion behaviour. The matrix of the A360lSiClxxp composites is virtually free of Ni and Cu while the A380/SiClxxp matrix contains 1.39-1.44 wt-%Ni and 3.13-3.45 wt-%Cu. The kinetics of the corrosion process were studied using gravimetric tests. The nature of corrosion products was analysed by SEM and low angle XRD before and after accelerated testing to determine the influence of microstructural changes on corrosion behaviour during exposure to the corrosive environment. The extent of the corrosion damage to the AllSiC composites depended on the concentration of nucleation sites and the matrix composition. One of these nucleation site is in the interlace region between the matrix and the particles. The corrosion process was influenced more by the concentration of alloy elements in the matrix than by the proportion of SiCp reinforcement.