The aqueous corrosion behavior of 0/90 cross-plied P130x graphite fiber reinforced 6063 Al composite laminates was studied in deaerated and aerated aqueous Na2SO4 and NaCl solutions using immersion and electrochemical techniques. Special emphasis was given to the identification of the principal mechanism(s) of corrosion. It was demonstrated conclusively via microscopic and electrochemical considerations that galvanic attack of the matrix was by far the dominant mechanism of corrosion in both solutions when Al and graphite are simultaneously exposed. Localized attack of microstructural segregations, if operative, was negligible compared to galvanic corrosion. When graphite is not exposed to the electrolyte, pitting of the surface foil, followed by galvanic attack of the matrix once the pit penetrates to the underlying graphite fibers, was found to be the primary corrosion mechanism. The effects of matrix heat-treatment, solution pH, sulfite ion contamination, and solution aeration on the electrochemical parameters and the overall corrosion behavior in 3.5% NaCl solutions were also studied. In general, the susceptibilities of general, galvanic, and localized corrosion were found to increase at lower pH levels and in the presence of sulfite ion contamination. Progressive aging of the matrix decreased corrosion susceptibility in deaerated solutions, but seemed to increase it in aerated solutions. The impact of each of the above parameters on the electrochemical nature of the various operative corrosion processes has been discussed in detail.