Abstract

Protection and maintenance processes are very important in the various sectors utilizing metallic materials. Protection routes can either be passive or active depending on the components of the coating material. Active corrosion protection for metallic substrates is being widely explored with the use of smart release coatings delivering corrosion inhibitors to defective sites upon damage of protective coatings. The incorporation of modified additives into polymers such as epoxy resins offers robust solutions and aims at maximizing the materials' compatibility for the fabrication of protective surfaces. The present investigation describes the contribution of neem phytochemicals as corrosion inhibitors loaded in biocompatible silica nanocontainers providing a protective primer to the corrosion process. The hybrid particles inside the organic matrix were pH-sensitive and the triggered release of encapsulated inhibitors was meant to provide a barrier in the coating defect from the aggressive corrosion-promoting environment. Crystallinity and morphology of the nanoparticles were characterized using XRD and TEM. Further characterizations were carried out using ATR-FTIR and TGA. The mesoporous silica nanoparticles prepared possessed a surface area of 867.3 m2/g, narrow pore size distribution (d ∼ 3 nm) and pore volume (∼ 0.5 cm3/g) as revealed by the N2 sorption measurements. These properties supported the loading and storage of the bio-based inhibitor. Two different solvents were explored in the inhibitor loading step. Active anticorrosive performance from an artificially scratched area of the investigated coatings was evaluated via electrochemical impedance spectroscopy (EIS). 2 wt.% of the inhibitor loaded nanocontainers was incorporated in the passive epoxy matrix resulting in a moderate distribution of the nanocontainers in the epoxy matrix. The presence of the bio-based corrosion inhibitor leveraged the anticorrosion performance of the modified epoxy coatings protecting Aluminium alloy 6061 in comparison to the unmodified epoxy coating. The antibacterial efficiency of the studied coatings was explored on the biofilm-forming bacteria Pseudomonas nitroreducens, a potential biofoulant.

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