PITTING CORROSION BEHAVIOR OF SIC/AL ALLOY MATRIX COMPOSITES

The corrosion behavior of SiC/Al Metal Matrix Composite (MMC) was investigated by polarization measurement and SEM observation. The behavior of SiC/Al MMC was the same as ordinary Al alloys as matrix materials. The anodic polarization curve of SiC/Al MMC in sodium borate-boric acid buffer solution (PH 8.39) containing sodium chloride was very similar to those of ordinary Al alloys. The pitting potential of SiC/Al MMC in each sodium chloride solution was almost the same as that of the ordinary alloys. This fact indicated that the existence of the SiC did not affect breakdown of the passive film. According to the observation at the SiC/Al interface of model composites which contain macroscopic boundaries, small pits occurred at random over the whole surface after anodic polarization. Occasionally a small number of pits appeared at SiC/Al interface, suggesting the preferential sites for pit growth.