Corrosion Performance of Newly Developed Al-Mg Alloys

The corrosion behavior of the newly developed Al-Mg alloys was investigated in terms of their alloying element and thermo-mechanical treatments by means of intergranular corrosion test, exfoliation corrosion test, scanning electron microscopy and transmission electron microscopy. The results show that, with the increase of Mg content the mass loss of the alloys in concentrated nitric acid increased, correspondingly their intergranular corrosion resistance decreases. Zn addition to the Al-Mg alloys led to the formation of Mg32(Al, Zn)49phase at the grain boundary, which dramatically increased the intergranular corrosion resistance of the alloys. The corrosion resistance of the alloys was also modified by thermo- mechanical treatment. Both intergranular corrosion resistance and exfoliation corrosion resistance of the alloys were dramatically increased by a proper post stabilizing treatment after cold rolling reduction. The residual stress, higher dislocation density and morphology of elongated grains after cold rolling reduction can lead to more continuous precipitation at the grain boundary, thus decrease the corrosion resistance of the alloys.