A comparative study of lithium salts for the corrosion inhibition of 2024 aluminium alloy

Abstract

In the present work, the corrosion inhibition of AA2024 by lithium salts (nitrate, oxalate and carbonate) is investigated by using both global and local electrochemical techniques. With LiNO₃ (0.1 M), the anodic and cathodic current densities are lower and the impedance values higher by comparison with the results obtained in the presence of 0.1 M Li₂C₂O₄ or 0.1 M Li₂CO₃. After 20 h of immersion in the electrolyte, SEM observations reveal the formation of thick films on the AA2024 surface in the presence of carbonate or oxalate, whereas a thin and denser film is formed in the presence of nitrate. Specifically, the Li₂C₂O₄ addition, by increasing the pH of the electrolyte, induces significant alloy dissolution from the very beginning of immersion which contributes to the growth of a protective layer on the alloy surface, combining lithium, carbonate species and metal cations.

A self-healing effect by Li₂C₂O₄ or Li₂CO₃ is shown by local impedance measurements on artificial scratches made on a water-based epoxy coating deposited on AA2024 plates, confirming their potential use, as inhibitive species, in organic coatings.