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Development of a Corrosion Protection Silica-based hybrid Sol-gel Coatings on Aluminum Alloys 2024-t3 by Encapsulating Benzimidazole and Octadec-9-enoic acid.
* 1, 2, 3 , 4 , 5 , 5
1  Mechanical and Energy Department, The Libyan Academy for Graduate study, Tripoli, Libya
2  Mechanical Engineering Department, Sok Alkhamis Imsehel High Tec. Institute, Tripoli, Libya
3  The Institute of Marine Engineering, Science And Technology, London, UK
4  Materials and Engineering Research Institute (MERI), Sheffield Hallam University, UK
5  Materials and engineering research institute, Sheffield Hallam university, united kingdom
Academic Editor: Julio A. Seijas (registering DOI)

Corrosion affects any metallic materials, such as pipelines, ships, and offshore platforms, as it is estimated that year’s corrosion losses are one-fifth of the global resources. The most efficient way of reducing the impact of this environment is using coatings- provision of barrier between the material and the aggressive environment. Hybrid Silica-based Sol-gel-derived coating presents one of the most viable pre-treatments alternatives to chromate. A significant advantage of the sol-gel process is the possibility of forming a hybrid inorganic-organic structure network at low temperatures. In addition, sol-gel coatings have good adhesion to metallic substrates and organic materials. Therefore, as a continuance of previous research on sol-gel coating systems. The work reports the performance of hybrid sol-gel formula formed from TEOS and MTMS enhanced by polysiloxanes with and without the presence of environmental benign corrosion inhibitor individually formed from benzimidazole (BZI) and Octadec-9-enoic acid (OA) as a duplex layers coating system. The sol-gel only and the duplex coating systems were at the same thickness, which can be applied to lightweight alloys such as aluminum alloy 2024-t3 to form a fundamentally corrosion inhibited and crack-free coating. The corrosion protection mechanism’s evaluation for these coatings is based on electrochemical tastings using potential-dynamic polarization scanning (PDPS) and electrochemical impedance spectroscopy (EIS). The protective properties of the coating system were studied when immersed in 3.5% NaCl to imitate the aggressive environment. The chemical confirmation was checked by infrared spectroscopy (FTIR), supported by analyzing surface morphology after 360 hrs. of immersion testing using scanning electron microscopy (SEM) and water contact angle for coated samples (WCA). The corrosion resistance performance of this coating system is a result of the combination of good adhesion, and pore blocking of the silica-based hybrid coating, and the presence of both encapsulated OA as a carrier and BZI as a film-forming volatile corrosion inhibitor resulting in durable film-forming, reducing the reaction at cathodic sites. Also, it exhibited excellent anti-corrosion properties, providing an adherent protective film on the aluminum alloy 2024-T3 samples compared to previous sol-gel and bare metals, which might last more than 60 days without any sign of failure, with an eco-friendly and cost-effective.

Keywords: hybrid silica-based sol-gel coating; electrochemical testing; corrosion protection; aluminum alloys; benzimidazole; Octadec-9-enoic