Recently, there has been increased interest in using aluminum alloys in ship construction instead of fiberreinforced plastic (FRP). Aluminum alloy ships are faster, have a greater load capacity, and are easier to recycle than FRP ships. We investigated the mechanical and electrochemical properties of aluminum alloys using slow strain rate and potentiostatic tests under various potential conditions. Aluminum and aluminum alloys do not corrode due to the formation of an anti-corrosive passive film, such as Al2O3 or Al2O3·3H2O, which resists corrosion in neutral solutions. In seawater, however, Cl. ions destroy this passive film. The optimum protection potential range with regards to hydrogen embrittlement and stress corrosion cracking was determined to lie between .1.5 and .0.7 V (SSCE). These results can be used as reference data for ship design.