The corrosion behavior of two nanocrystalline bulk Cu-50Ag alloys prepared from hot pressing powders which were synthesized by liquid phase reduction or mechanical alloying was investigated in acidic solutions as compared with the corresponding coarse grained Cu-50Ag alloy. Results show that the corrosion rates of the three alloys become faster after H2SO4 is added to Na2SO4 solutions. The corrosion rates of PMCu-50Ag and LPRCu-50Ag alloys remain unchanged, but those of MACu-50Ag alloy become faster with the increment of H2SO4 solution concentrations. In Na2SO4 solutions, there are no passivation phenomena for three Cu-50Ag alloys. On the contrary, there are passivation phenomena after H2SO4 is added to Na2SO4 solutions. The corrosion rates of three Cu-50Ag alloys increase in the order of PMCu-50Ag, LPRCu-50Ag and MACu-50Ag alloys. The rates of LPRCu-50Ag alloy are slightly higher than those of PMCu-50Ag alloy, but are evidently lower than those of MACu-50Ag alloy. In Na2SO4 solutions, EIS of three alloys are composed of single capacitive loops. There are diffusion tails after H2SO4 is added to Na2SO4 solutions. This indicates the corrosion processes are controlled by diffusion.