Immersion tests and electrochemical experiments were performed to study the room temperature corrosion behavior of the unmodified and modified Al-Cu alloys with using RExOy (Pr-x,O-y and La-x Oy) in 3.5 wt.% NaCl solution and pH = 4 acid solution. The results showed that the modified Al-Cu alloys have superior corrosion resistance than the unmodified alloy in both solutions. However, a contrary variation trend of corrosion resistance with increasing REx O-y content was found in these two solutions. In 3.5 wt.% NaCl solution, the corrosion resistance of the modified alloys increases gradually with increasing RExOy content, but deceases gradually in pH = 4 acid solution. The reason for this contrary trend was discussed. (c) 2014 Elsevier B.V. All rights reserved.