One-pot synthesis of polybenzoxazine resin in situ blended with nano extract Lawsonia inermis as a shield coating for C-Steel in acidic environment: Experimental and theoretical approaches

This study examines the impact of Lawsonia inermis L. ( Henna ) nano extract as a novel, environmentally, and naturally occurring addition on resin coatings made using in situ polybenzoxazine ( PBZ ). The resin coatings formulated with different ratio of Henna as a shield protection for carbon steel (C-Steel) in 1 M HCl electrolyte. Here, Henna was extracted using a three-hour reflux in bi-distilled water. Since lawsone is the primary constituent of Henna , it undergoes nanoscale grinding, dynamic light scattering (DLS) confirmation, and FTIR and SEM analysis to determine its ultimate structure. Benzoxazine ( BZ ) was polymerised in situ using varying Henna mixing ratios (3, 5, and 7 wt%). The application and curing of the coated resin on C-Steel panels was followed by an investigation into the impact of varying ratios of Henna extracts on the thermal, mechanical, morphological, and weathering accelerator properties. Scanning electron microscopy (SEM) were used to examine the surface conditions of the coated C-Steel substrates. Potentiodynamic polarisation (PDP), electrochemical impedance spectroscopy (EIS), and salt-spray corrosion valuation methods were employed to assess the anticorrosive efficacy of PBZ/ Henna composite coatings on C-Steel in 1 M HCl electrolyte. When the amount of PBZ/ Henna in the samples is increased, the mechanical qualities and thermal stability both improve with Henna loading. There is a discernible drop in the corrosive solution movement velocities over the coated cross-section following 500 hours of exposure to the salt spray test. According to electrochemical experiments, the addition of Henna to the coat mixture provides additional protection, and the more Henna used, the higher the efficiency. Quantum chemical simulations of the PBZ/ Henna composite show the highest E HOMO , lowest E LUMO , and largest corrosion inhibition efficiency, which are in good accord with the experimental results. Furthermore, the PBZ/ Henna composite bonded to the steel surface more effectively than PBZ alone, according to molecular dynamic (MD) simulations analysis. • Henna is used to modify PBZ to improve its anti-corrosion performance. • The PBZ/ Henna composite improves the coated protection properties. • Electrochemical studies prove PBZ/ Henna composite supports protection efficiency. • Quantum calculations for PBZ/ Henna have the highest E HOMO and lowest E LUMO .