Improved corrosion resistance of mild steel in HCl solution with a CuI–lawsone complex

• N.A. Basim Abd¹, H. Sheerali¹ and M. Nasr-Esfahani²

¹ Faculty of pharmacy, Jabir Ibn hayyan university for medical and pharmaceutical science, Najaf, Iraq
² Department of Chemistry, Na.C., Islamic Azad University, Najafabad, Iran

Abstract: A reduction in the toxicity of corrosion inhibitors can be effectively achieved through the use of green inhibitors. While henna extracts show good inhibition in dilute, cold HCl, the impact of CuI on inhibition efficiency is unknown. This study investigates CuI’s effect on lawsone from henna leaves as a corrosion inhibitor for mild steel in 5% HCl at 30℃ and 60℃ using weight loss, potentiodynamic polarization (PDP), electrochemical impedance (EIS), scanning electron microscopy (SEM), energy-dispersive X-ray (EDX), atomic force microscopy (AFM), Fourier transform infrared (FTIR), and UV-vis spectroscopy. For this purpose, three corrosion inhibitor solutions (CIS) including Lw (CIS-L), CuI (CIS-C), and Cu-Lw complex (CIS-LC) were prepared in dimethylformamide (DMF) solvent. The formation of Cu-Lw complex in CIS-LC was monitored by FT-IR, and UV-Vis. Results indicate that the inhibition efficiency of CIS-LC is higher than CIS-L and can reach 94.4% when 3% CIS-LC is used, while CIS-C merely causes a copper-like brown color change in MS specimens and does not provide sufficient corrosion protection. The SEM/EDX observations show that the MS specimen surface is undamaged and covered with a protective coat formed by Cu-Lw from CIS-LC. CuI and henna extract work synergistically to inhibit corrosion of mild steel in 5% HCl.

Keywords: acidizing, green corrosion inhibitor, lawsone, mild steel, CuI

Int. J. Corros. Scale Inhib., 2025, 14, no. 4, 1813-1831
doi: 10.17675/2305-6894-2025-14-4-5

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