Active corrosion protection of aluminium AA2024-T3 with corrosion inhibitor loaded electrospun nanofibres
An exploratory study and proof of concept
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Abstract
Aluminium AA2024-T3 is a high strength aluminiumalloy widely used in aerospace. The strengthening copper-rich intermetallic phases, however, make the material very susceptible to aqueous corrosion and severe pitting. To protect the metal, coatings loaded with corrosion inhibitors are typically used. Traditionally, highly efficient CrVI-based inhibitors have been used but these are soon to be banned due to their high genotoxicity. The use of alternative environmentally friendly inhibitors is commonly bound to the problem of incompatibility with the organic coating matrix. As a solution to reduce unwanted inhibitor-matrix reactions and to control the inhibitor release extensive research has been devoted to the development of responsive inhibitor nanocarriers. These carriers are, however, limited in the amount of inhibitor they can store thereby having a narrowpotential for long-term protection at damage sites such as scratches or cracks. Alternative concepts are therefore needed. This work explores for the first time the use of responsive electrospun polymeric nanofibers loaded with corrosion inhibitors as an efficient carrier system for long termprotection of relatively big damages in coated AA2024 structures. For the proof of concept explored in this work, water soluble poly(vinyl alcohol) fibres loaded with up to 10 wt% CeCl3 were successfully electrospun. To control the inhibitor release the PVA fibres were crosslinked at different degrees by glutaraldehyde. The influence of fibre chemistry and inhibitor loading on the release kinetics of the loaded fibre mats was investigated via in-situ UV/VIS spectroscopy. Loaded fibremats were successfully incorporated in a protective epoxy/amine coating system varying the position of the inhibiting mat within the coating with respect to the substrate. Insitu opto-electrochemical impedance spectroscopy was used to investigate the long-term, protective, self-healing behaviour of the prepared coating systems after damage. Protection up to 4 weeks was achieved for several coating compositions with different fibre chemistries and corrosion inhibitors. This research opens the path for the development of sophisticated, tailored and highly efficient inhibitor delivery systems for the protection of metal structures at large damages for long immersion times.