Laterally-resolved formation mechanism of a lithium-based conversion layer at the matrix and intermetallic particles in aerospace aluminium alloys

Lithium leaching coatings have recently been developed as eco-friendly active corrosion protection technology for aerospace aluminium alloys (AAs) by the formation of a conversion layer at coating defects. While general characteristics were studied and reported before, here we study local process with sub-micron resolution around intermetallic particles (IMPs) in AA2024-T3. Top- cross-sectional-view morphological electron micrograph observations along open circuit potential (OCP) measurements are performed, mimicking defect conditions upon lithium carbonate from matrix. The results revealed five stages which alloy matrix different IMPs evolve morphologically, compositionally, electrochemically. Besides, found correlation between OCP response AA2024-T3 system compositional evolutions exposure. Passive dissolution leading to surface Cu-enrichment S-phase dealloying occur early They precede columnar on alloy, followed establishment dense-like final stage. Dealloying Al2CuMg can assist providing supersaturation. Through complementary experiments sodium solution besides X-ray diffraction analysis, out that plays critical role stabilising product throughout process.