Agricultural waste of tobacco stem extract as a novel and efficient inhibitor for the corrosion of steel in HCl solution

This study focuses on the extraction and evaluation of tobacco stem extract (TSE) as a novel corrosion inhibitor for promoting the efficient utilization of waste tobacco stems in agricultural systems and developing a highly effective, eco-system friendly corrosion inhibitor for cold-rolled steel (CRS). TSE was prepared using a simple and cost-effective reflux extraction method. Experimental studies and theoretical calculations were conducted to test its corrosion inhibition performance on CRS in hydrochloric acid (HCI) media. The findings indicate that TSE exhibits unique properties with an optimum inhibition efficiency of 91.1 % at 40°C. The adsorption of TSE on CRS surface follows Langmuir isotherm. Polarization curves demonstrate that TSE acts as a mixed-type inhibitor through “geometric covering effect” mechanism, while mainly retarding the cathodic reaction. As the concentration of TSE increases, the charge-transfer resistance significantly rises leading to increased inhibition efficiency. Micrograph tests confirm that adding TSE in HCI-aggressive solution efficiently prevents corrosion of CRS substrate. XPS analysis reveals the presence of Fe-O, C O, C-O and C-N peaks on the outer layer of CRS, confirming the formation of effective films. TOF-SIMS confirms hydrocarbon correlation peaks on inhibited CRS surface along with significant N atoms and Fe correlation bonds observed in both positive and negative ion spectra, verifying effective adsorption of TSE molecules onto inhibited CRS surface. Various components contribute to corrosion inhibition by TSE with quercetin and nicotine being primary active agents located primarily in aromatic ring, C-O, and N heterocycles sites. Molecular dynamics simulations demonstrate excellent inhibition performance as quercetin and nicotine can adsorb nearly flat onto Fe (001) surface. • Tobacco stem extract (TSE) is a highly effective inhibitor for steel in HCl with the maximum inhibition efficiency of 90 %. • TSE inhibits both cathodic and anodic reactions through the “active site blocking effect” mechanism. • TSE forms a protective film on CRS surface that is confirmed by MM, SEM, AFM, CLSM, XPS and TOF-SIMS. • Quercetin and nicotine are the main active ingredients in TSE with a nearly parallel manner.