The electrochemical behavior of an Al-Cu-Li alloy

ABSTRACT

Al-Cu-Li alloys present interesting advantages over conventional Al-Cu-Mg alloys used in the aerospace industry, due to their excellent properties, such as high fatigue resistance and low density. The mechanical properties of these alloys depend on their microstructure. In this work, the electrochemical activity associated with the microstructure and corrosion behavior of the AA2198-T8, Al-Cu-Li alloy, was investigated through electrochemical and immersion tests, in chloride ions (Cl^–) containing solutions. Results obtained showed that the electrochemical behavior and susceptibility to corrosion of this alloy are strongly influenced by the T1(Al₂CuLi) phase density which is mainly responsible for its hardening. It was also observed that this phase is electrochemically more active than the aluminum matrix and when exposed to corrosive environments, it results in severe localized corrosion (SLC), due to crystallographic attack. In these regions, intense acidification was observed, within the pits, resulting in hydrogen gas evolution, which was confirmed by gel visualization tests. The results obtained through global electrochemical techniques and scanning vibrating electrode technique (SVET) confirmed the observations from the immersion and gel visualization tests, where increased values of anodic current densities were related to the SLC regions.

Keywords:
Al-Cu-Li alloys; Severe localized corrosion (SLC); Electrochemical Techniques; Scanning Vibrating Electrode Technique (SVET)