Corrosion prevention of AA2024-T3 aluminum alloy with a polyaniline/poly (γ-glycidoxypropyltrimethoxysilane) bi-layer coating: Comparative study with polyaniline mono-layer feature

In this work, we report a comparative study of the physicochemical properties, particularly the anticorrosion performance of coatings deposited onto AA2024-T3 surface, namely a mono-layer coating of polyaniline (Pani) and a bi-layer one consisted of an inner Pani layer and an external poly(gamma-glycidoxypropyltrimethoxysilane (Poly (gamma-GPTMS)) layer (Pani/Poly(gamma-GPTMS)). For both coating types, Pani was electrodeposited onto AA2024-T3. Poly(gamma-GPTMS) layer was applied by dip-coating onto Pani to form the bi-layer coating. Scanning Electron Microscopy (SEM), Fourier Transform Infrared Attenuated Total Reflectance (FTIR-ATR) and Ultraviolet-Visible spectrophotometry (UV-Vis) proved the successful synthesis of coatings. For Pani/Poly(gamma-GPTMS), formation of hydrogen bonds between layers was proved. Poly(gamma-GPTMS) layer has filled defects of Pani network, where metallo-siloxane bonds, were established. Pani/Poly(gamma-GPTMS) coating revealed better adhesion, water repellency and anticorrosion performance than Pani. Electrochemical Impedance Spectroscopy (EIS) demonstrated that the Poly(gamma-GPTMS) layer served as an effective physical barrier top-coat against the penetration of corrosive species through the Pani layer. Poly(gamma-GPTMS) improved hence, the anticorrosion performance of coating system for a longer exposure period in chloride medium.