Synergistic Effect of Potassium Iodide on Corrosion Inhibition of Carbon Steel by Achillea santolina Extract in Hydrochloric Acid Solution

The aim of this study is to examine Achillea santolina extract (ASE) as a green inhibitor for carbon steel (CS) in corrosive medium (1.0 M HCl) under different experimental conditions. This investigation occurs by using mass loss (ML), open-circuit potential, potentiodynamic polarization (PP), electrochemical frequency modulation (EFM), AC impedance spectroscopy (EIS), energy-dispersive X-ray spectroscopy (EDX), scanning electron microscopy (SEM), and atomic force microscopy (AFM). The inhibition efficiency (%IE) enhanced by rising of ASE dose and also, with temperature increasing. The addition of 0.01 M KI to 1.0 M HCl solution containing ASE decreases the corrosion of CS and improves the performance of ASE by a synergistic effect. The presence of the iodide ions improves the surface film formed on the surface of CS. The inhibition effect of the ASE on the CS surface was confirmed by EDX, SEM, and AFM analysis. This work represents the first use of ASE as an effective green corrosion inhibitor.