EFFECT OF SCANDIUM ON THE CORROSION BEHAVIOR OF THE CASTING Al - Cu ALLOYS IN NACL SOLUTION

Corrosion behavior of the casting Al - Cu alloys with and without Sc addition was studied by both the immersion test and electrochemical measurement methods. The results show that pitting corrosion was found on the surfaces of these alloys in 3.5 wt .% NaCl solution, while the corrosion resistance of the Al - Cu alloys with Sc is better than that of the Al - Cu alloy without Sc . With increasing Sc content, the corrosion resistance of the present Al - Cu alloys varies significantly, and the 0.1 wt .% Sc alloy has the best corrosion resistance. Also, the corrosion potential of the present alloys with Sc is shifted positively compared with that of the alloy without Sc by electrochemical measurement, indicating that the alloys with Sc have better corrosion resistance. The microstructures of the Al - Cu alloys change from the coarse grains to the fine equiaxed grains due to Sc addition, which is responsible for the reduced susceptibility to corrosion and the enhanced corrosion resistance of the present alloys.