Abstract: Li-Al LDHs/BTC composite coating was prepared on 6063 aluminum alloy by hydrothermal method. The film's composition, morphology, and corrosion resistance were studied by Fourier transform infrared spectroscopy (FT-IR), scanning electron microsocope(SEM), and electrochemical methods. The results showed that BTC was filled into the LDH lamellar gap and was distributed on the coating surface, so the composite coating showed high compactness. The electrochemical test show that the corrosion current density of Li-Al LDHs/BTC composite coating decreases by 2 and 1 orders of magnitude compared with blank aluminum alloy and pure Li-Al LDH, respectively. Meanwhile, the charge transfer resistance of the coating is 2 orders higher than that of Li-Al LDH, which indicates the Li-Al LDHs/BTC composite coating has good corrosion resistance. The enhanced corrosion resistance may be that the addition of BTC makes the composite coating denser.
Aluminum alloy has good mechanical properties, high specific strength, and low density, widely used in shipbuilding, aerospace, and other fields. But the chemical properties of aluminum alloy are very active, easy to occur pitting corrosion, intergranular corrosion, crevice corrosion, stress corrosion, and other corrosion phenomena, affecting its use. The researchers used surface treatment to improve the corrosion resistance of aluminum alloys. Chemical conversion treatment is low-cost and easy to operate and is widely used in the corrosion-resistant treatment of aluminum alloy, among which the chromate conversion method is the most widely used. However, hexavalent chromium in the chromate conversion membrane will cause harm to the environment and human body and has been banned by many countries. Therefore, chromium-free chemical conversion treatment has become a research hotspot.
Layered double hydroxides, also known as hydrotalcite or hydrotalcite-like compounds, are ordered by the interaction of a positively charged main layer with the anions between the layers through covalent bonds. Because of its unique interlayer anion exchangeability and laminate controllability, it has been widely used in the field of corrosion prevention in recent years.
The metal-organic framework has a uniform distribution of active metal nodes, controllable channels, ultra-high porosity, and a variety of coordination environments, which can easily prepare a variety of different structures. It has been widely used in gas adsorption, sensing, and catalysis, but there are few related types of research in the field of corrosion prevention.
The LML/BTC composite coating was successfully prepared on the surface of 6063 aluminum alloy by hydrothermal method. The electrochemical test found: Compared with the blank aluminum alloy and the aluminum alloy covered with LML film, the corrosion current density of the aluminum alloy covered with LML/BTC composite coating is 3.5wt.% NaC1 solution is decreased by 2 and 1 orders of magnitude, respectively, and the charge transfer resistance is increased by 2 orders of magnitude compared with the sample covered with LML film. It indicates that LML/BTC composite coating can reduce the corrosion rate of 6063 aluminum alloy and improve the corrosion protection performance of the aluminum alloy matrix. At the same time, we found that LML/BTC composite coating has a long-term corrosion protection effect on aluminum alloy.
