Cleome arabica L. extract as a novel green corrosion inhibitor for AISI 1045 carbon steel in 0.5 M HCl: insights from experimental and theoretical DFT analyses

The search for sustainable, cost-effective and environmentally friendly corrosion inhibitors for hydrochloric acid (HCl) solution in industrial applications has garnered increasing interest in plant extracts and their refined metabolites. In this research, Cleome arabica L. (CA) extract, found in the Algerian Sahara, was considered due to its low cost compared to other studied plants and higher content of active compounds, thereby emerging as a promising candidate and offering the potential to promote a circular economy model. This study assessed the effectiveness of CA extract as a green corrosion inhibitor for AISI 1045 carbon steel in 0.5 M HCl solution and highlighted its potential to advance the field of green corrosion inhibitors. ATR-FTIR and LC-ESI-MS/MS analyses revealed the presence of significant organic compounds, including coumaric acid (74.58%), 4-methoxybenzoic acid (12.53%), and kaempferol (8.05%), which contributed to the corrosion inhibition. The inhibitory effectiveness of the CA extract was evaluated at five concentrations, ranging from 0.125 to 1 g L⁻¹, using weight loss measurements, potentiodynamic polarization (PDP) and electrochemical impedance spectroscopy (EIS). The highest inhibition efficiency (η = 94.45%) was observed at a CA extract concentration of 1 g L⁻¹ after 196 hours of immersion in 0.5 M HCl. Thermodynamic analysis using the Langmuir adsorption isotherm yielded a ΔG_ads value of −24.737 kJ mol⁻¹, indicating the spontaneous adsorption of CA molecules onto the AISI 1045 surfaces, forming a protective layer, which was confirmed by SEM/EDX analysis. Density functional theory (DFT) calculations showed a significant correlation with the experimental data, confirming that CA extract is a highly efficient and environmentally friendly corrosion inhibitor.