Review of the state of art of Li-based inhibitors and coating technology for the corrosion protection of aluminium alloys

The quest for novel alternatives to hexavalent-chromium-based corrosion inhibitors is of utmost significance and urgency. Strict international health and safety regulations, due to growing concerns regarding the impact of hexavalent chromium on human health and the environment, have pushed the commercial introduction of many alternative...

Spatiotemporally resolved corrosion protection of AA2024-T3 by a lithium-based conversion layer

In this work, the corrosion mechanism of AA2024-T3 covered by a lithium-based conversion layer is studied with high spatial and temporal resolution. Although the aluminium alloy surface is protected by a multi-layered conversion layer, areas around intermetallic phases (IMPs) represent weak spots due to an insufficient generation of a...

The effect of pH on the corrosion protection of aluminum alloys in lithium-carbonate-containing NaCl solutions

The corrosion inhibiting effect of lithium carbonate has been studied over the pH range relevant for atmospheric corrosion conditions at the polymer/metal interface. It is demonstrated that lithium carbonate offers optimum corrosion protection under moderately alkaline conditions attributed to the formation of a protective layer identified as...

The Effect of Ambient Ageing on the Corrosion Protective Properties of a Lithium-Based Conversion Layer

The influence of ageing under ambient conditions on the corrosion protective behaviour of a lithium-based conversion layer on AA2024-T3 is studied in this work. Conversion layers aged at ambient conditions for relatively short times (0 h and 4 h), show an initial high degree of corrosion inhibition but a much lower protectiveness after the...

Local scanning electrochemical microscopy analysis of a lithium-based conversion layer on AA2024-T3 at progressive stages of formation

Scanning electrochemical microscopy (SECM) is employed to characterize the evolution of local electrochemical surface activity during lithium-based conversion layer formation on legacy aerospace aluminium alloy AA2024-T3. Initially, three types of studied intermetallic particles - S-, θ- and constituent phases - act as active cathodic areas....

Evaluation of the formation and protectiveness of a lithium-based conversion layer using electrochemical noise

The formation process of a lithium-based conversion layer on AA2024-T3 and its corrosion protective behavior are studied using electrochemical noise (EN). Wavelet transform, as well as noise resistance analysis, have been employed to interpret the EN data. The EN data confirmed five different stages during the conversion layer growth,...

In-situ nanoscopic observations of dealloying-driven local corrosion from surface initiation to in-depth propagation

Dealloying is involved in materials science responsible for fabrication of nanoscale structures beneficially but for corrosion degradations detrimentally. Detailed understanding related to the latter is critical for designing corrosion-resistance alloys and dedicated inhibition systems. Thus, direct nanoscopic observations of nano-structural...

Dealloying-driven local corrosion by intermetallic constituent particles and dispersoids in aerospace aluminium alloys

Nanoscopic characterization of heterogeneous intermetallic particles (IMPs) which microstructurally and compositionally evolve during local corrosion is crucial in unravelling the mechanisms and sequence of initial and local corrosion events. Herein, we study site-specific initiation events focused on microscopic constituent intermetallic...

Active corrosion protection of aerospace aluminium alloys by lithium-leaching coatings

For decades, scientists and engineers are searching for a safe and environmentally friendly alternative for the toxic chromate corrosion inhibitors in active protective coatings for the protection of aerospace aluminium alloys. In this search many different compounds have been investigated as leachable corrosion inhibitor, but no alternative...

The chemical throwing power of lithium-based inhibitors from organic coatings on AA2024-T3

Chemical throwing power, being the distance over which an inhibitor is able to protect a defect effectively, is an important parameter for active protective coatings. This study investigates the chemical throwing power of lithium-based leachable corrosion inhibitors exhibiting different leaching kinetics, from coatings at different inhibitor...

Active corrosion protection of various aluminium alloys by lithium-leaching coatings

This study presents the active protective properties of lithium-leaching coatings for a range of aluminium alloys. Coatings with and without lithium carbonate as leachable inhibitor were applied on the aluminium alloys, artificially damaged and exposed to the neutral salt spray. A combined approach of scanning electron microscopy and...

On the importance of irreversibility of corrosion inhibitors for active coating protection of AA2024-T3

Inhibitor leaching, fast, effective and irreversible passivation are essential for active protective coatings to protect aluminium alloys. This study presents the comparison of the active protective properties of lithium carbonate and two organic corrosion inhibitors, benzotriazole and 2-mercaptobenzothiazole, on aluminium alloy 2024-T3 with...

Compositional study of a corrosion protective layer formed by leachable lithium salts in a coating defect on AA2024-T3 aluminium alloys

Organic primer coatings loaded with environmentally harmful Cr(VI) corrosion inhibitive pigments still play an important role in corrosion protection of aluminium alloys for the aerospace industry. A potential “green” alternative coating system has recently been developed, loaded with lithium salt corrosion inhibitors. Under exposure to...

Electrochemical evaluation of corrosion inhibiting layers formed in a defect from lithium-leaching organic coatings

This work presents the electrochemical evaluation of protective layers generated in a coating defect from lithium-leaching organic coatings on AA2024-T3 aluminum alloys as a function of neutral salt spray exposure time. Electrochemical impedance spectroscopy was used to study the electrochemical properties on a macroscopic scale. An...

Protective film formation on AA2024-T3 aluminum alloy by leaching of lithium carbonate from an organic coating

An investigation into corrosion inhibition properties of a primer coating containing lithium carbonate as corrosion inhibitive pigment for AA2024 aluminum alloy was conducted. It was found that, during neutral salt spray exposure, a protective film of about 0.2 to 1.5 ?m thickness formed within the area where an artificial defect was introduced...