Multifunctional graphitic carbon nitride/manganese dioxide/epoxy nanocomposite coating on steel for enhanced anticorrosion, flame retardant, mechanical, and hydrophobic properties

Abstract

Benzidine (Bz) was used to modify the nanofiller, manganese dioxide (MnO2), and the resulting Bz/MnO2 was then encased in pure epoxy resin (EP) with graphitic carbon nitride (GCN). The effectiveness of epoxy-coated mild steel in protecting against varying concentrations of GCN/Bz-MnO2 was assessed through the use of electrochemical techniques in natural seawater. The flame retardancy capabilities of the epoxy coating were significantly improved by the incorporation of GCN/Bz-MnO2. The EP-GCN-Bz/MnO2 nanocomposites display peak heat release rate (PHRR) and total heat release (THR) values which are 79 % and 62 % lesser than that of pure EP, respectively. When compared to a pure epoxy coating, the results of salt spray tests indicated that the addition of GCN/Bz-MnO2 improved corrosion protection and decreased water absorption. Electrochemical impedance spectroscopy (EIS) studies showed that the epoxy-GCN/Bz-MnO2 coating still had an improved resistance of 6.40E10 Ω.cm2 even after 30 days of exposure to seawater. Scanning electrochemical microscopy (SECM) displayed lowest ferrous ion dissipation (1.0 I/nA) in the EP-GCN/Bz-MnO2 nanocomposite coated steel. Potentiodynamic polarization testing showed that EP-GCN-Bz/MnO2 had a lower current density (icorr: 0.03 µA/cm2) in comparison with other coatings. This is mainly because the Bz alteration of the MnO2 nanoparticles and their successful coordination with GCN sheets result in a noticeably more compact nanostructure that lowers aggregation and increases binding capacity. Surface-modified GCN was found to be improved in its breakdown products, leading to the production of a strong, inert nanolayered covering, according to Scanning electron microscopy with energy dispersive X-ray spectroscopy (SEM/EDX) analysis. Water contact angle (WCA) of 160° demonstrates the exceptional water resistance of the recently developed EP-GCN/Bz-MnO2 coating. In terms of hardness and adhesion strength, Bz/MnO2 wrapped in GCN had good mechanical characteristics on the epoxy substrate. The improved adhesive strength (18.3 MPa) for mild steel coated with EP-GCN/Bz-MnO2 was attained prior to being immersed in seawater. The EP-GCN/Bz-MnO2 crystallizes form a robust, inert coating that prevents ions from accessing the specimen. The coating has increased adhesive strength as a result, and it can withstand deep immersions without losing its integrity. Hence, the EP-GCN/Bz-MnO2 nanocomposite might work as a useful coating component in the automotive industry.