ALDC8 alloy was often corroded with form of intergranular corrosion in corrosive environments. Thus in order to improve its corrosion, the effect of annealing to corrosion resistance and hardness was investigated with parameters of heating temperatures such as 100°C, 200°C, 300°C, 400°C and 500°C for 1hr. Hardness was slightly decreased with annealing, especially, the decreasing of hardness was remarkably revealed in annealing temperature at 300°C. Corrosion potential was shifted to noble direction, and both AC impedance at 10m㎐ and polarization resistance on the cyclic voltammogram was also increased with annealing. Intergranular corrosion was not nearly observed at annealing temperature of 400°C, 500°C. Therefore the optimum annealing temperature for corrosion resistance as well as mechanical property is thought to be 400°C or 500°C.