Electrochemical characterization of the aluminum-lithium 2099 alloy with different heat treatments.

Al-Li 2099 alloy is considered third generation due to its low density, high stiffness and corrosion resistance, so it is used in aeronautical structures that require high mechanical strength because they are subjected to great stresses in flight conditions, such as fuselage and wing stringers. These alloys have presented an anisotropy problem in the mechanical properties, due to the lithium content, which can be reduced with a heat treatment process. Then, to optimize the mechanical properties and corrosion resistance it is important to control the thermal process. The objective of this study is to determine the effect of heat treatments for aging in the presence of localized corrosion in aluminum-lithium 2099-T83 exposed in H₂O, 3.5% NaCl, 1% HCl and 2% H₂SO₄. The heat treatments TO and T6 were carried out for the Al-Li 2099-T83 alloy and a T6 heat treatment for the 2024-TO alloy. It was characterized electrochemically with the potentiodynamic polarization and Electrochemical Noise technique based on ASTM G61 and ASTM G199, respectively. The results showed that the alloy 2099-T83 has a lower corrosion rate in all corrosive medium. The 2024-T6 and 2099-TO in all the medium presented localized corrosion, for the 2099-T6 and T83 in H2O, NaCl, HCl presented localized corrosion, and for the case of the medium H₂SO₄ generalized corrosion occurred for the last two treatments. For the Electrochemical Noise results, it shows that the Al-Li 2099 presents nobler potentials than the 2024. Finally it can be concluded that the 2099-T83 and T6 presents greater resistance to corrosion than in the conventional aluminum (2024) that is they use today in aeronautical structures helping in the selection of materials for design and weight savings in aircraft.