Abstract
In the present work, nanostructured graphene nanosheets were added to hybrid silica sols and deposited on aluminium alloy A2024-T3 to study the effect on the corrosion behaviour. Sols were prepared using tetraethyl-orthosilicate (TEOS), 3-glycidoxypropyl-trimethoxysilane (GPTMS) and a colloidal silica suspension (LUDOX) as silica precursors with adding chemically modified graphene nanosheets (GN-chem). The graphene nanosheets were modified through a straightforward and simple hydrothermal approach and then, dispersed into a silica sol (SiO2/GN-chem). ATR-FTIR was used to optimize the silica sol–gel synthesis and to confirm the cross-linking of the silica network. The corrosion behaviour of the SiO2/GN-chem coatings was also analysed by electrochemical measurement (potentiodynamic polarization) in 0.05 M NaCl solution. The results showed that the incorporation of modified graphene nanosheets into hybrid silica sol–gel coatings affected the corrosion properties of the substrates. An improvement in the corrosion resistance was observed likely due to the enhanced barrier property and hydrophobic behaviour obtained by incorporation of GN-chem and colloidal silica nanoparticles.
Highlights
Aluminium alloys such as AA2024-T3 and AA7075-T6 are mainly used in aircraft and automotive industries due to their excellent strength to weight ratio
The chemical modification of graphene nanosheets (GN) was studied by Attenuated Total Reflectance (ATR)-Fourier transform Infrared (FTIR) and Raman spectroscopies
To the best of our knowledge, this is the first time that the synthesis protocol of silica sols based on introduction of graphene nanosheets with colloidal SiO2 nanoparticles is reported
Summary
Aluminium alloys such as AA2024-T3 and AA7075-T6 are mainly used in aircraft and automotive industries due to their excellent strength to weight ratio. Silica-based sol–gel coatings deposited on aluminium substrates have demonstrated good adhesion and corrosion protection performance through forming stable Si-O-Al chemical bonds between the silica layer and the substrate [4]. The incorporation of graphene oxide (GO) nanosheets in coatings for enhancing the corrosion properties has been studied in recent years. Liu et al [9] reported the preparation of thin graphene coatings on aluminium alloys by direct deposition of GO from aqueous solution with effective anticorrosion barrier properties. The characterization showed that C-O-Si bonds formed, enhancing the cross-linking density of the network and improving the corrosion protection of aluminium alloys
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