Eco-friendly corrosion inhibition of steel in acid pickling using Prunus domestica Seeds and Okra stems extracts

Abstract

The corrosion inhibition process during acid pickling in petroleum industries often employs toxic chemicals, facing stringent environmental regulations. This study explores a sustainable alternative by investigating the inhibitory effects of eco-friendly food waste extracts, namely Prunus domestica seeds (P.S) and Okra stems (O.St), on B7 grade steel corrosion in 1.0 M HCl aqueous solution, simulating an acid pickling environment. The corrosion inhibition efficiency was estimated via both electrochemical methods, including electrochemical impedance spectroscopy and potentiodynamic polarization techniques, and chemical methods, such as weight loss measurements. Fourier transform infrared spectroscopy (FTIR) and Gas chromatography-mass spectrometry (GC-MS) elucidated the extracts' main functional groups and potential chemical constituents. Remarkably, both extracts exhibited a maximum inhibitory efficiency of up to 80 %. Adsorption isotherms were employed to analyze the inhibition mechanisms, including Langmuir and Flory–Huggins models, alongside the Kinetic-thermodynamic model. Activation parameters have been obtained using Arrhenius and transition state equations. The synthesis of the activated complex is characterized as an endothermic process, as evidenced by the positive values of enthalpy of activation (ΔH*). Conversely, negative entropy of activation (ΔS*) values indicate that the activated complex signifies a process of association rather than separation. Quantum chemical calculations identified potential active inhibitor compounds within the extracts. The quantum parameters, including ionization potential, electronegativity, softness, and hardness of the chemical constituents of the extracts, were calculated using DFT with the B3LYP/6–31 G(+) method. This study underscores the innovative approach of utilizing waste food extracts as corrosion inhibitors, addressing environmental concerns while offering practical implications for industrial applications.