In situ nano silver-imbosed cardanol-based polyurethane nanomaterial as protective coating of mild steel: Synthesis, characterization, antibacterial and anticorrosive analysis

A novel approach to fabricate sustainably room temperature cured silver-doped cardanol (COL) based advanced polyurethane nanomaterial (CAgPU@PNM) coating without any catalyst, curing agent, or crosslinker. The work aims to replace conventional petroleum-derived polyurethanes by aligning with green and sustainable development principles. Coatings cured under ambient conditions were developed, and their properties were evaluated. The structural confirmation was achieved through Fourier-transform infrared (FTIR) spectroscopy performance, along with X-ray diffraction (XRD) Field-emission scanning electron microscopy (FE-SEM) and Transmission electron microscope (TEM) techniques were used to investigate the morphology of the semi-crystalline polymer nanocomposites with uniformly dispersed Ag nanostructures. Atomic Force Microscopy (AFM) revealed a moderately rough surface (17 nm) and formation of a hydrophobic surface. The incorporation of Ag was corroborated by EDX analysis. Mechanical test was checked by Pencil-Hardness, Cross-Hatch, Impact-Resistance, and Bending whereas, chemical stability (for 4 months) has been investigated under various chemical environments (3.5% HCl, NaOH, NaCl, and water). Polyurethane formulation enhances thermal stability as compared to the pristine material as evaluated using Thermogravimetric analysis (TGA) and Derivative thermogravimetry (DTG) analysis. The water contact angle (138°) revealed that the surface is hydrophobic. In conjunction with Nyquist and Bode plots, EIS spectroscopy was utilized to study corrosion inhibition (in 3.5 wt% NaCl solution) for 24 days. The Nyquist and Bode plots indicate that these coatings serve as effective corrosion inhibitors, characterized by elevated Rc, Rs, and CPE values. Furthermore, antibacterial studies were conducted against gram-negative bacteria (K.pneumoniae and P.aeruginosa) and gram-positive bacteria (S.aureus and B.subtilis), and antifungal activity against C. albicans fungi was assessed, suggesting potential applications in antibacterial coatings for commercial use.