Effect of Sc Addition on Corrosion Behavior of As-cast Al-3Cu-1Li Alloy in Acidic NaCl Solution

Abstract:

The effect of Sc addition on the corrosion behavior of as-cast Al-3Cu-1Li alloy in 2 mol/L NaCl acidic solution was studied. The phase compositions of as-cast Al-3Cu-1Li-xSc (mass fraction) alloys were determined by XRD. The microstructures of Al-3Cu-1Li alloy and Al-3Cu-1Li-0.5Sc alloy were observed by FE-SEM/EDS and TEM. The corrosion behavior of the alloy was studied by potentiodynamic polarization, EIS, EN and immersion test, and the corrosion mechanism was discussed. The results show that Cu-rich spherical phases are distributed in the grain of Al-Cu-1Li alloy; Cu-rich spherical phase is reduced, and W phase precipitates at the grain boundary of Al-3Cu-1Li alloys containing Sc. Sc can reduce the corrosion reaction activation energy of the alloys, making the corrosion process easier. With increasing the Sc content, cathode hydrogen evolution rate increases, the self-corrosion current density of the alloy increases, and the corrosion resistance decreases gradually. EN and EIS results show that the surfaces of Al-3Cu-1Li alloy and Al-3Cu-1Li-0.1Sc alloy are in the state of “film rupture-repassivation” during 12 h immersion in the solution, and Al-3Cu-1Li-0.3Sc alloy and Al-3Cu-1Li-0.5Sc alloy have severe intergranular corrosion.

Key words:Sc-containing Al-Cu-Li alloy;acidic NaCl solution;W phase;Cu-rich phase;electrochemical noise