Corrosion Behavior of Welded Joints

The corrosion behavior of an Al-6Mg-Sc-Zr alloy was studied and compared with that of an Al-6Mg-Zr alloy. The addition of scandium into the Al-6Mg-Zr alloy reduced the susceptibility to exfoliation corrosion. By using the constant load tensile method in a 3.5 wt.% NaCl solution, the resistance to SCC of the Al-6Mg-Sc-Zr alloy was higher than that of the Al-6Mg-Zr alloy. When the specimens were not applied with an anodic current, the Al-6Mg-Sc-Zr alloy was resistance to SCC and no brittle cracking was found on the fracture surface. When an anodic current was applied, the Al-6Mg-Sc-Zr alloy specimens failed as a result of accelerated corrosion rather than SCC. It was believed that the addition of scandium resulted in (Al3Sc, Zr) particles that greatly refined grains and promoted the formation of homogeneous discontinuous distribution of β-phase in the alloy base, which much contributed to good corrosion resistance of the Al-6Mg-Sc-Zr alloy.