Pitting corrosion growth characteristics of aluminum alloys in the solution containing SO₄^2- ion

Abstract

To investigate the pitting corrosion growth rate of aluminum alloys in the solution containing SO₄^2- ion, the immersion corrosion test and electrochemical measurements were carried out on aluminum and Al–0.4%Cu alloy clad with the liner containing Zn. In the solution containing SO₄^2- ion the pitting corrosion could grow deeply even in the alloy having gradient of Zn concentration. While Cl^- and SO₄^2- ions concentrated into the pit, SO₄^2- ion had little effect on electrochemical characteristics in acidified higher chloride solution. The pitting potential of aluminum became much less noble with as a little addition of Zn as 0.2%, but that of Al–Cu alloy scarcely varied in acidified higher chloride solution. As the SO₄^2- ion had the controlling effect of pitting corrosion density, which introduced higher chloride ion concentration in a pit. Therefore, for the control of pitting corrosion growth rate the potential slope had to be sharper in the solution containing SO₄^2- ion. Enough Zn content at surface was required to obtain better pitting corrosion resistance, especially in Al–Cu alloy.