Effect of Minor Alloying Elements on Corrosion Resistance of Al-Zn-Mg Alloy Welds(Materials, Metallurgy & Weldability)
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An investigation has been made of the effect of minor alloying elements on the corrosion resistance of Al-Zn-Mg alloy welds using a commercial Al-Zn-Mg alloy (7N01) and four kinds of Al-Zn Mg alloys separately added 0.05% Ti, 0.2% Fe-0.1% Si, 0.5%Mn and 0.2%Cr by means of the pitting potential of anodic polarization curve and electrical resistivity measurement. The pitting potential in anodic polarization curve was related to the resistivity showing the solution of the minor alloy in the matrix rather than the weight percent of minor alloying addition. The addition of 0.05% Ti to the Al-Zn Mg alloy hardly shows the increase of the resistivity, and hardly affects the age hardening characteristics and pitting potential. The addition of 0.2%Fe-0.1%Si to the alloy hardly shows the increase of the resistivity, and hardly affects the pitting potential, but markedly affects the age hardening characteristics at 120℃. The addition of 0.5%Mn to the alloy causes the markedly increase of the resistivity, and markedly causes the increase of the pitting potential for aged specimen but hardly affects the age hardening at 120℃. The addition of 0.2%Cr to the alloy affects both age hardening characteristics and the pitting potential. The age hardening at 120℃ hardly occurs by the addition of Cr, but the pitting potential is improved. The pitting potential depends on not only the amount of minor alloying elements but also the solution treatment temperature. As the relatively insoluble compounds is fairly solutionized in the matrix at 560℃ solution temperature, the solute concentration of Cr increases in the matrix, and then the pitting potential increases and becomes more noble.
- Transactions of JWRI
Transactions of JWRI 14 (2), 305-311, 1985-12