Study on Corrosion Behavior of Friction Stir Welded Joints of Aluminum/Copper Dissimilar Metals
The welding of 6061-T6 aluminum alloy with thickness of 3 mm and T2 pure copper was realized by friction stir welding technology.The macro forming,electrochemical corrosion and immersion corrosion behaviors of the Al/Cu joints were investigated.The results show that the Al/Cu friction stir welding joint is well formed,and no cracks,holes and other defects are observed.The corrosion potential of Cu is higher than that of Al,leading to the formation of macroscopic galvanic couples between Al/Cu.The corrosion potential of the Al/Cu joints is lower than that of the two base metals,and the corrosion current density is greater than that of the two base metals.The macroscopic galvanic effect in the joints promotes the corrosion of the joints.Within 24 h of immersion,the corrosion of the joint mainly occurs on the aluminum alloy side,among which the corrosion of the heat affected zone on the aluminum side is the most serious,resulting in larger corrosion pits.Local pitting corrosion also occurs in the nugget zone of aluminum side and the aluminum base material,with a relatively light of corrosion.The corrosion products on the aluminum surface is Al(OH)3/Al2O3.
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