Corrosion Resistance of Li-Al LDHs Film Modified by Methionine for 6063 Al Alloy in 3.5 wt.% NaCl Solution

Abstract

Methionine(Met) was introduced to modify the Li-Al layered double hydroxides (LDHs) film prepared on 6063 aluminum alloy by in situ method for the first time. Fourier transform infrared spectroscopy, X-ray photoelectron spectroscopy, Scanning electron microscopy, and X-ray diffraction confirmed the successful insertion of Met into LDHs film and revealed that the introduction of Met could make the LDHs film much denser. Electrochemical tests illustrated that the corrosion rate of the Met modified LDHs film was reduced by more than an order of magnitude compared with the bare Al alloy. Moreover, the corrosion rate of the modified LDHs film after immersion in 3.5 wt.% NaCl solution for 21 days was almost the same as that without immersion, which indicates that the modified film has good corrosion durability. The corrosion resistance of the scratched modified film could recover to the level without a scratch on the 14th day based on the scratch test results, meaning the modified film has a good self-healing property. Finally, the anti-corrosion mechanism of the Met was proved by molecular dynamic simulations and found that the enhanced corrosion resistance may be attributed to the addition of Met that slowed the diffusion of the corrosive medium Cl− and water molecules.

Preparation and Applications of Superhydrophobic Coatings on Aluminum Alloy Surface for Anti-Corrosion and Anti-Fouling: A Mini Review

“…However, the aluminum alloy covered with Zn-Al LDH-VO x film did not have noticeable corrosion pits even after one month of immersion, which indicated that, compared with the traditional hydrothermal method, the LDH film prepared by electrodeposition is thicker, but it has better corrosion resistance. Besides, there are also studies [11] using a hydrothermal method and ion exchange method to obtain methionine-modified Al-Li-Met LDH film on the surface of 6063 aluminum alloy, which found that this film layer reduces the corrosion current density of aluminum alloy in 3.5 wt.% NaCl by one order of magnitude compared with blank aluminum alloy. However, it can also automatically restore its original morphology and structure after external mechanical scratches, showing particular self-healing performance and improving its corrosion protection durability.…”

“…The droplet on the solid surface, explained by the Cassis-Baxter model, is a heterogeneous wetting state, because the air is trapped in a rough groove below the droplet, preventing it from penetrating the groove and forming an air cushion. The preparation of superhydrophobic coatings on the surface of aluminum alloys can not only effectively prevent direct contact between the corrosive medium and the matrix but also significantly shorten the residence time of pollutants or corrosive media on its surface, and inhibit the formation of continuous electrolyte film on the surface of the coating, thereby playing the dual role of anti-corrosion and anti-fouling (self-cleaning) on the aluminum alloy substrate [9][10][11]. In this review, we first summarized the types of anti-corrosion and anti-fouling coatings on aluminum alloy surface and their advantages and disadvantages.…”

Intrinsic Self-Healable, Corrosion-Resistant Silicone Coating Based on Quadruple Hydrogen-Bonded Supramolecular Polymer

“…Self-healing coatings have been rapidly developed in recent years, and many strategies have been explored, including microcapsules, − reversible cross-linking, and chemical or physical reactions. − The microencapsulated self-healing coating, which has been widely studied, can release the healing agent to occupy the damaged area in the coating. At present, most microcapsules present excellent healing behavior typically in the initial period; however, it is restrained by the release performance and the corresponding adsorption or filling property for the long-term.…”