Experimental and theoretical approaches to examine the effects of Bupleurum montanum extracts as corrosion inhibitors on carbon steel in an acidic solution

This study investigated the effect of n-butanol (BE) and ethylacetate (EAE) extracts from the Bupleurum montanum to prevent carbon steel (CS) corrosion in 1.0 M HCl using gravimetric analysis, EIS and PDP methods, theoretical modeling, and surface characterization research. The inhibitory effect was directly proportional to extract concentration and inversely related to temperature. Both BE and EAE displayed optimal inhibitory efficacy at specific concentrations. At a 1000 ppm concentration, BE obtained a peak inhibition level of 87.12%, while EAE displayed an optimal inhibition of 83.32% at 900 ppm, both under a temperature of 283 K. The study evaluated the influence of temperature variations on corrosion rates, specifically within the temperature range of 283–323 K. Each test needed five (5) hours of immersion. The extracts were physisorbed on steel surfaces and obeyed Freundlich’s model. In order to comprehend the inhibitory mechanism, the calculations were performed to determine the energy of activation (Ea) and significant thermodynamic properties that explain the process’s kinetics and thermodynamics. The parameters imply a significant interaction involving the chemical inhibitor and the metal surface, which needs physical adsorption. In acidic conditions, both EAE and BE demonstrated significant corrosion inhibition, acting as mixed-type inhibitors with efficiency levels reaching 81.29–85.60% (EIS) and 84.96–85.73% (polarization) at varying concentrations. SEM analysis revealed that Bupleurum montanum extract components, when adsorbed onto the metal surface, created a smoother surface with less damage. Furthermore, the theoretical results backed up the idea that the inhibitor binds to the steel surface at specific reactive locations. In an acidic condition, this study successfully identified Bupleurum montanum extract (BME) as a good and green corrosion inhibitor for CS.