THE CORROSION BEHAVIOUR OF Al-13.5Si-9Mg/SiC_p COMPOSITES IN CHLORIDE SOLUTIONS INVESTIGATED WITH ELECTROCHEMICAL TECHNIQUES

摘要

The influence of retained porosity on the corrosion behaviour in a 0.1M NaCl solution of particulate-reinforced metal matrix composites (MMC) obtained by the pressureless infiltration method, has been investigated. The composites consisted of an Al-13.5%Si-9%Mg alloy matrix, and silicon carbide particles (SiC_p) reinforcement. Electrochemical tests were carried out for two composites one with low and one with high retained porosity. Results of cyclic polarization measurements indicated that the composite with the higher retained porosity had a more negative value of pitting potential (E_p), thus suggesting that it was more susceptible to pit corrosion. Localized corrosion in these composites seems to initiate in the Al-alloy matrix, preferably in porous regions of the surface.