The corrosion resistance of graphite/aluminum (Gr/Al) and silicon carbon/aluminum (SiC/Al) metal matrix composite (MMC) materials and composite corrosion protection methods were investigated in marine environmental exposures ranging from 30 to 365 days. Accelerated corrosion of the Gr/Al resulted from galvanic interactions between the graphite fibers and the aluminum matrix. Corrosion of the SiC/Al was due to pitting, which was oriented at the silicon carbide-aluminum interfaces in the discontinuous forms of silicon carbide reinforcement. Differences in surface foil alloy and composite structure for the Gr/Al or type of silicon carbide reinforcement for the SiC/Al did not affect the materials' overall corrosion resistance. A variety of corrosion control coatings was found to be suitable for protection of the MMC, including organic and thermal-sprayed coatings.