The microstructure and corrosion initiation sites of a particulate alumina reinforced 6092 Al metal-matrix composite (MMC) were examined with scanning electron microscopy and energy-dispersive X-ray analysis (EDXA). The MMC was embedded with a variety of Ti-containing microparticles that were likely introduced into the Al matrix as impurities of the alumina reinforcements. When the MMC was immersed in either 0.5 M Na2SO4 or 3.15 wt % NaCl solution in open-circuit conditions, microcrevices formed around the Ti-containing particles as well as the Fe-Si-Al intermetallic particles. With the semiquantitative EDXA technique, the Ti-containing particles that induced the microcrevices can be roughly divided into three categories: (i) titanium suboxides with compositions close to that of Ti6O, Ti3O, Ti2O, and TiO, (ii) Ti-Zr-Al oxides, and (iii) TiO2. Although little is known about the electrical properties of the titanium suboxides and the Ti-Zr-Al oxides, the results suggested that these compounds were either electrically conducting or semiconducting. Microcrevices also formed around some particles with an oval structure. The core region of the oval structure appeared to be a Ti-Si-Al phase, while the shell region of the oval structure appeared to be an Fe-Si-Al phase.