Synergistic Effect of KI on Corrosion Inhibition of Carbon Steel by Myrrh Gum Extract in Sulfuric Acid Solution

This study explores, for the first time, the synergistic effect between myrrh gum extract (MG) and iodide ions to enhance corrosion inhibition for API 5CT P110 tubing steel in 0.5 mol/L sulfuric acid. The interaction between MG and iodide ions was analyzed using potentiodynamic polarization curves, electrochemical impedance spectroscopy, scanning electron microscopy, and energy-dispersive X-ray spectroscopy. Results show that the inhibition efficiency of 6 g/L MG at 20°C is 82%, but it significantly increases to 98% upon adding 5 mmol/L potassium iodide at 20°C. The system follows the Langmuir adsorption isotherm, involves both physisorption and chemisorption, and functions as a mixed-type inhibitor. The findings confirm that the combination of Ghars date extract and iodide ions provides substantial corrosion protection for API 5CT P110 tubing steel in sulfuric acid through a synergistic effect.