Sol-gel/MOF nanocomposite for effective protection of 2024 aluminum alloy against corrosion

In this work, MIL-53 (Al) nanoparticles were synthesized and then were characterized by SEM, EDS, FTIR, TGA, and BET techniques. Afterwards, the nanoparticles were incorporated in hybrid (TEOS + GPTMS) sol-gel coating as nano-filler and the obtained nanocomposite was applied on Al 2024 alloy. Micro-sized defects were disappeared from surface of the coating after addition of the nanoparticles. Uniform distribution of the nanoparticles in the matrix of the sol-gel coating was confirmed by TEM. Also, average roughness of the coating was reduced from 76 to 17 nm after addition of the MIL-53 (Al) nanoparticles. Thermal stability of the sol-gel coating was improved by the nano-particle incorporation. The FTIR method was also successfully used to confirm the chemical interaction between the incorporated nanoparticles and the silica coating. The results of the EIS tests in Harrison's corrosive media indicated that the corrosion resistance of the sol-gel coating was remarkably enhanced after incorporation of the MOF nanoparticles in 1 g L-1 concentration so that the polarization resistance of the nanocomposite coating was about 68 times higher than the neat coating after 24 h immersion. This result was attributed to the chemical interaction between the silica matrix and embedded nanoparticles and so, formation of more compact silica structure.