Electrochemical and surface analyses of metal complexes as corrosion inhibitors for carbon steel in 1 M HCl environment

• H.F. Emrayed¹, H.M. Hasan¹, B.M. Eisay², H.S. Khatab³, E.M. Jibreel³, M.M. Amrajaa³ and A.S. Fouda⁴

¹ Department of Chemistry, Faculty of Science, Omar Al-Mukhtar University, Albyda, Libya
² Libyan Academy for Postgraduate Studies, Al Gabal Alakhder branch, Libya
³ Department of Chemistry, Faculty of Education, Almarj, Benghazi, Libya
⁴ Department of Chemistry, Faculty of Science, Mansoura University, Mansoura-35516, Egypt

Abstract: In this study, the synthesis and evaluation of the corrosion inhibition performance of Hg(Phe)₂ and Cu(Phe)₂ complexes on carbon steel (CS) in 1 M hydrochloric acid solution were investigated at different temperatures ranging from 25 to 55°C. The experiments include weight loss measurements (WL), electrochemical methods (impedance spectroscopy, EIS and potentiodynamic polarization, PDP). According to the electrochemical test results, these compounds exhibit moderate corrosion-inhibition performance, with Cu(Phe)₂ and Hg(Phe)₂ achieving inhibition efficiencies of 88.6% and 89.8%, respectively, at a concentration of 11·10^–6 M. The findings also show that the two inhibitors’ inhibitory impact grew as inhibitor concentration increased, indicating that these substances strongly adsorb to the steel surface. The adsorption of the two complexes fits to the Langmuir adsorption isotherm. Since the values were found to be between –20.1 and –26.1 kJ/mol, the analyzed isotherm plots demonstrated that the adsorption process for these complexes on CS surface is a mixed-type inhibitor. The presence of a protective film on CS surface is confirmed by using scanning electron microscopy (SEM), energy dispersive X-ray (EDX) spectroscopy and atomic force microscope (AFM). The ability of the two inhibitors to stop CS from corroding in 1 M HCl, displace water molecules from CS, and create heterogeneous coatings on the CS surface to prevent corrosion was supported by quantum chemical calculations. Experimental and surface examination findings were in good agreement.

Keywords: corrosion inhibition, carbon steel, Hg(Phe)2, Cu(Phe)2, metal complexes, HCl

Int. J. Corros. Scale Inhib., 2026, 15, no. 3, 244-269
doi: 10.17675/2305-6894-2026-15-3-10

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