Corrosion characteristics of aluminium based metal matrix composites

There is a growing demand both in aerospace as well as commercial markets for lighter weight, higher stiffness and higher thermal stability materials to solve the design engineer's problems of reduced mass, higher access speeds, improved mechanical and thermal stability for today's advanced technologies. Metal matrix composites satisfy the above mentioned properties. However, corrosion is a major concern as the secondary phase formation in the matrix takes place as a result of ceramic particle addition, which threatens their exploitation for such applications. In the current paper, the corrosion characteristics of different aluminium based metal matrix composites of varying volume fractions of SiC (SiC/Al) has been studied systematically. Pitting corrosion studies have been investigated in detail. Scanning electron microscopy (SEM) has been used not only to understand the nature of corrosion but also to identify the location of corrosion in the matrix phase. X-ray diffraction analysis (XRD) has been used to determine the intermetallics formation. EPMA studies have been carried out to determine the distribution of SiC particulates in the matrix as well as the location of intermetallics. Finally, the corrosion mechanism causing the SiC/Al composites to degrade under marine environmental conditions has been presented and the necessity of finding suitable surface coatings to enhance the corrosion resistance of these composites is stressed.