<i>Duranta erecta</i> Fruit and Leaf Extracts as Green Corrosion Inhibitors for Mild Steel Protection in Hydrochloric Acid

Recently, green corrosion inhibitors have emerged as a promising alternative to synthetic inhibitors for protecting the metal surface in acid-based industries due to their lower cost, eco-friendliness, and nontoxic nature. In this work, Duranta erecta plant organs were used to develop D. erecta fruit extract (DEFE) and D. erecta leaf extract (DELE). These extracts were characterized by liquid chromatography–mass spectrometry (LC–MS) and Fourier transform infrared (FTIR) analyses and added to the MS specimens immersed in 1 M HCl. The inhibitive effect was examined by weight loss and electrochemical methods. Outcomes revealed that D. erecta extracts have an effective corrosion-controlling potential for mild steel (MS) corrosion in HCl. The corrosion inhibitory effect of both DEFE and DELE was increased with their dosage up to 200 mg L–1 but decreased with the temperature. The highest corrosion inhibitory efficacies, 90.8% and 91.8%, were achieved at 303 K with 200 mg L–1 of DEFE and DELE, respectively. Kinematic parameters (Ea, ΔH#, and ΔS#) were determined using potentiodynamic polarization (PDP) data of the following temperature range: 303–323 K, which implies that MS degradation becomes difficult in the presence of inhibitors. An acid attack on the metal surface in the presence and absence of inhibitors was also examined by using field emission scanning electron microscopy (FESEM), energy-dispersive X-ray (EDX), and atomic force microscopy (AFM) analyses, and the results were consistent with the findings of the corrosion test.