4. Discussion

The 2050-T84 alloy with additional lithium was developed to have improved mechanical properties to be applied to aircraft structural components. The results of potentiodynamic potential shows that this alloy requires less amount of energy yielded for rupture of the oxide layer, however, once corrosion is started its evolution is rapid. Corrosion process occurred near precipitates T<sup>1</sup> and T<sup>2</sup> that increases to more positive values, causing matrix dissolution. However, the presence of the lithium to weight reduction and increase of mechanical resistance due to the appearance of precipitate T<sup>1</sup> and free zones precipitate. In cryogenic conditions, this material presents retention of ductility and fracture toughness, due to the facecentered cubic crystal structure (FCC) and the and the freezing of impurities with low melting point and rich in hydrogen (H), sodium (Na) and potassium (K), dispersed in the Al matrix.

Fatigue corrosion behavior of this material indicates that the competition between hydrogen embrittlement and the plasticity induced by salt crystals and cracking tip oxides are beneficial for FCG. This behavior occurs for to process of crack growth being purely mechanical and the corrosion products formed within the crack lead to contact between the surfaces by raising the crack closing tension intensity factor.
