Steel corrosion in acidic environments is a critical industrial challenge, necessitating effective yet eco-friendly inhibitors. This study aims to address this problem by introducing a novel, green alternative: frankincense extract (FE). The distinctive contribution of this work lies in the comprehensive investigation of FE natural, sustainable, and economically viable resin as an effective corrosion inhibitor for carbon steel in 1 M HCl. The research employs an integrated methodology, including electrochemical techniques (potentiodynamic polarization (PDP) and electrochemical impedance spectroscopy (EIS)), adsorption isotherm modeling, surface analysis (FT-IR and FESEM/EDX), and density functional theory (DFT) calculations. Key results demonstrated that FE exhibited excellent inhibition performance, achieving a remarkable efficiency of 87.2% at a concentration of 16 g/L and 303 K. PDP analysis confirmed FE acts as a mixed-type inhibitor. EIS results corroborated this performance, showing 75.89% inhibition efficiency. Adsorption behavior adhered to the Langmuir isotherm, and thermodynamic parameters revealed a spontaneous and exothermic process indicative of mixed physisorption and chemisorption mechanisms. Kinetic studies further supported this by showing an increased activation energy barrier for corrosion in the presence of the inhibitor. Surface analysis confirmed the formation of a protective adsorbed film on the steel. Quantum chemical computations provided molecular-level insights, correlating the electronic structure of key FE constituents with their adsorption strength. The study establishes FE as a cost-effective, sustainable, and highly efficient green corrosion inhibitor, offering a viable solution for protecting carbon steel infrastructure in aggressive acidic media.
