Effects of Artificial Aging and Corrosion Medium Concentration on Electrochemical Corrosion Behavior of 2A97 Al-Cu-Li Alloys

Abstract:

The corrosion resistance of 2A97-T3 and 2A97-T6 Al-Cu-Li alloys was studied by the electrochemical method through potentiodynamic polarization curves. The typical third generation 2060-T8, 2099-T83, and 2024-T4 alloys were used as reference for comparison. Through the analysis of electrochemical parameters and corrosion morphology, the results reveal that the corrosion resistance of the alloys in NaCl solution of different concentrations is as follows: 2A97-T3>2A97-T6>2024-T4>2060-T8>2099-T83. With increasing the concentration of NaCl solution, the corrosion potential (E_Corr) of all alloys is decreased. Moreover, the surface pitting and intergranular corrosion become severe. The T₁ phase greatly increases with more uniform distribution in 2A97-T6 alloy, which is obtained from the 2A97-T3 alloy after the solid solution coupled with double-stage artificial aging treatment. Consequently, the heat treatment process reduces the corrosion potential of 2A97-T6 Al alloy, which leads to the slightly weaker corrosion resistance of 2A97-T6 Al alloy than that of 2A97-T3 alloy. The disintegration of the intergranular θ phase induces the exfoliation corrosion morphology of 2A97-T3 alloy, and the pitting morphology of 2A97-T6 alloy is caused by the dissolution of intragranular T₁ phase.

Key words:Al-Cu-Li alloy;electrochemical polarization;corrosion potential;heat treatment;corrosion morphology