Eco-Friendly Corrosion Inhibition of OLC45 Steel in H2SO4 Solution Using Rhus typhina L. Plant Extracts

This study focuses on the evaluation of eco-friendly corrosion inhibitors derived from extracts of Rhus typhina L. leaves, collected in August during the summer season, on OLC45 metal surfaces in a 0.5 M H2SO4 corrosive environment. The extracts were obtained using the microwave extraction technique and characterized by HPLC. The protective properties of OLC45 coated with LESRT (leaf extract collected in summer from Rhus typhina L.) were examined by potentiostatic and potentiodynamic polarization procedures and electrochemical impedance spectroscopy (EIS) in 0.5 M H2SO4. The application of the Langmuir isotherm revealed high values of the adsorption constant and standard free energies (ΔG°ads), suggesting a possible mixed adsorption process with an increased tendency toward chemisorption. The influence of temperature on the electrochemical behavior of OLC45 samples in H2SO4, both in the absence and presence of two extracts derived from Rhus typhina leaves at a concentration of 1000 ppm, was investigated over the temperature range of 293–333 K. A comparison of the two inhibitors’ effectiveness revealed high inhibitory efficiency, up to 91% at 1000 ppm LESRT1 (methanol/double-distilled water (50%:50%, v/v)) and 92% for LESRT2 (ethanol/double-distilled water (50%:50%, v/v)) at 1000 ppm LESRT2.