Hybrid NiO nano rods-quantum carbon dots composites as a novel corrosion protective coating on EN3 mild steel in the marine environment

This research endeavors to synthesize nickel oxide nanoparticles (NiO NPs) using a sonochemical process facilitated by a nitrate precursor and alkaline sodium hydroxide (NaOH). In parallel, carbon dots (CDs) were derived from lemon waste peels via a facile hydrothermal method. Subsequently, the reflux method fabricated nickel oxide- carbon dot nanocomposite (NiO/CDs) in a 5:1 ratio. The structural properties, including crystallography, crystallinity, particle size, and morphology, were comprehensively characterized using X-ray diffraction (XRD) and high-resolution transmission electron microscopy (HRTEM). The synthesized nanoparticles exhibit excellent dispersion, with mean particle sizes of approximately 36.46 nm for NiO NPs and 2.17 nm for carbon dots. The carbon dots defect ratio (ID/IG) characteristics feature was estimated as 0.94 using Raman spectroscopy. NiO, CDs, and NiO/CDs nanocomposite coating were developed using a doctor blade method on the EN3 mild steel specimens. Electrochemical impedance spectroscopy was conducted in marine water conditions with 3.5 wt% of NaCl and seawater to evaluate the stability of the nanostructured coating. Electrochemical analysis, such as the Nyquist plot, Tafel plot, and frequency response finding, demonstrated that NiO/CDs nanocomposite coating has enhanced corrosion protection in 3.5 wt% NaCl solution compares to seawater medium. These findings underscore the potential of the NiO/CDs nanostructured coating to extend the lifespan of industrial mild steel (EN3) specimens in seawater environments.