Developing a Benzimidazole Silica-Based Hybrid Sol-gel Coating with Significant Corrosion Protection on Aluminum Alloys 2024-T3

The inherent reactivity of the Al-Cu-Mg alloys is such that their use for building structural, maritime, and aeroplane components with great strength/weight ratio, it would not be possible without good anti-corrosion systems. These systems could be considered as imitations of the protection mechanism found with the conventional hexavalent chromium-based system, but also limiting the environmental impact, precisely without toxic or carcinogenic effect, and should also be eco-friendly. Silica-based hybrid protective coatings have been shown to exhibit excellent chemical stability combined with the ability to reduce the corrosion of metal substrates. However, research shows that sol-gel has some limitation in term of the period of anti-corrosive properties. Therefore, this work reports the performance of a silica-based hybrid sol-gel coating encapsulated with Benzimidazole (BZI) that can be applied to light alloys to form a crack-free coating. This coating was applied on AA 2024-T3 and cured at 80ºC. The high corrosion resistance performance results from the combination of good adhesion, the hydrophobic property of the silica-based hybrid coating and the presence of the encapsulated (BZI) film-forming volatile corrosion inhibitor, which will be released at pores within the coating system resulting in film-forming, reducing the cathodic reaction at cathodic sites. The evaluation of this mechanism is based upon using electrochemical testing techniques. The anti-corrosion properties of the coatings were studied immersed within 3.5% NaCl by using electrochemical impedance spectroscopy (EIS) and Potential-dynamic polarization scanning (PDPS). The chemical confirmation was done by infrared spectroscopy (ATR-FTIR). supported by analyzing the morphology of the surface before and after the immersion testing by using scanning electron microscopy (SEM). The Benzimidazole-silica-based hybrid coating exhibited excellent anti-corrosion properties, providing an adherent protection film on the aluminium alloy 2024-T3 samples compared to sol-gel-only and bare material, with cost-effective and as an eco-friendly system.