The Effect of Ti and REE Addition on the Corrosion Resistance of the AlZn12Mg3.5Cu2.5 Alloy in "Acid Rain" Environment

Abstract

A significant problem associated with the use of high-strength aluminum-zinc alloys is their insufficient resistance to corrosion. A often used method of improving the resistance to corrosion is plating, resulting in a decrease of their strength. Improving the corrosion resistance can be achieved by application of micro - alloying elements. Titanium and rare earth elements are particularly interesting micro - alloying elements. Subject of examination were AlZn12Mg3.5Cu2.5 base alloy (without micro-alloying) and alloy with the addition of titanium alloy and alloy with the addition of rare earth elements. Corrosion examinations were carried out in a solution of "acid rain", pH = 3.5. The scope of the research included potentiodynamic and potentiostatic tests , examination of the surface and structure of the samples after corrosion.The research found that the addition of titanium does not cause a significant improvement in corrosion resistance of the AlZn12Mg3.5Cu2.5 alloy. A significant improvement was achieved with the addition of rare earth elements. It was found that corrosion tested alloys is local and leads to the formation of pits.

Research Status and Prospective Properties of the Al-Zn-Mg-Cu Series Aluminum Alloys

“…In addition, adding Ce to Al-Zn-Mg aluminum alloy could significantly prolong the stress corrosion cracking time and reduce the stress corrosion sensitivity. When 0.04% (mass fraction) Ce was added to Al-Zn-Mg aluminum alloy, Ce atoms and Al atoms could be oxidized simultaneously to form rare-aluminum composite oxide film (Al 2 O 3• Ce 2 O 3 and (Al,Ce) 2 O 3 ) [77], which improved the resistance of passivation film, significantly reduced the self-corrosion current density, and significantly improved the corrosion resistance of the alloy [78]. The addition of 7.5% (mass fraction) Y in aluminum alloy could greatly improve the degree of grain refinement and dislocation density.…”