The Synergistic Effect of Pomegranate Peel Extract with Zn²⁺, Ce³⁺, and KI Inhibition of Mild Steel Corrosion in Hydrochloric Acid: A Comparative Electrochemical and Surface Study

This study aims to evaluate the efficacy of pomegranate peel extract The study investigated the effect of (PPE) in reducing the corrosion of mild steel in a 1 M hydrochloric acid solution, as well as the effect of adding Zn²⁺, Ce³⁺ and KI enhances inhibition efficiency. Weight loss tests were conducted at various temperatures and immersion times, along with electrochemical measurements using open-circuit potential (OCP) , potential polarization, and electrochemical impedance spectroscopy (EIS). Surface characterization was performed using scanning electron microscopy (SEM), atomic force microscopy (AFM), and four-dimensional infrared (FTIR) spectroscopy. The weight loss results showed that increasing the PPE concentration from 200 to 600 ppm improved inhibition efficiency, reaching approximately 30.03% at 600 ppm. Combining PPE with additives also resulted in a significant improvement in inhibition efficiency. The best result was achieved with the PPE-KI system at a concentration of 600 ppm PPE and 2 mM KI, reaching an inhibition efficiency of  74.77%. This was followed by the PPE-Ce³⁺ system and then the PPE-Zn²⁺ system. The study of the effect of temperature and immersion time showed that 25 °C and 24 hours represented the optimal conditions for the PPE-KI system under investigation. Electrochemical measurements supported this trend; the PPE-KI system recorded the highest charge transfer resistance (Rct) of 107.20 Ω·cm², with an EIS-calculated inhibition efficiency of 69.22%. Furthermore, surface images showed improvement in the presence of PPE, particularly with the addition of KI, while FTIR spectra revealed changes in the environment of some functional groups after immersion. Overall, the results suggest a potential synergistic effect between PPE and KI.