Synthesis, spectroscopic characterization, and corrosion inhibition performance of a novel Schiff base for carbon steel in hydrochloric acid

• J.B. Normurotov¹, U.Ch. Akhmedov², M.U. Karimov³, I.S. Majidov³, N.A. Khusanov⁴, U.M. Berdiyarov¹, H.A. Zikirov¹, Sh. Abdumuratova⁵, Sh.I. Umarov⁶ and Sh.Sh. Esanov⁷

¹ Department of Chemical Engineering, Termez University of Engineering and Agrotechnology, Termez 190111, Uzbekistan
² Termez State University, Termez 190100, Uzbekistan
³ Tashkent Research Institute of Chemical Technology, Tashkent 111116, Uzbekistan
⁴ Tashkent State Technical University named after Islam Karimov, Tashkent, 100095, Uzbekistan
⁵ Department of Microbiology, Public Health, Hygiene and Management, Termez Branch of Tashkent State Medical University, Termez 190111, Uzbekistan
⁶ Department of Chemistry, Jizzakh State Pedagogical University, Jizzakh 130100, Uzbekistan
⁷ Tashkent State Medical University, Tashkent 2100109, Uzbekistan

Abstract: A novel Schiff base corrosion inhibitor (SB-1), N,N′-bis(4-(dimethylamino)benzylidene)-1,4-phenylenediamine, was synthesized via the condensation reaction of p-phenylenediamine with p-dimethylaminobenzaldehyde. The synthesized compound was comprehensively characterized by FT-IR, ¹H NMR, ¹³C NMR, HSQC, HMBC, DEPT, and ¹H–¹⁵N HMBC spectroscopy, confirming the successful formation of the target Schiff base structure. The corrosion inhibition performance of SB-1 toward St20 carbon steel in 1.0 M HCl solution was evaluated using gravimetric and potentiodynamic polarization (PDP) techniques. The results demonstrated that the inhibition efficiency increased with increasing inhibitor concentration, reaching 95.79% at 150 mg·L^–1 according to PDP measurements. Gravimetric analysis also revealed excellent inhibition efficiencies of up to 95.18% at elevated temperature, indicating enhanced adsorption of SB-1 on the steel surface. The small shift in corrosion potential (<100 mV) suggested that SB-1 acts as a mixed-type corrosion inhibitor, suppressing both anodic metal dissolution and cathodic hydrogen evolution reactions. The high inhibition efficiency is attributed to the adsorption of the Schiff base molecules through the azomethine groups, tertiary amine nitrogen atoms, and π-electron-rich aromatic rings, leading to the formation of a compact protective film on the steel surface. These results demonstrate that SB-1 is a promising corrosion inhibitor for carbon steel in acidic media.

Keywords: Schiff base, corrosion inhibitor, carbon steel, hydrochloric acid, potentiodynamic polarization, NMR spectroscopy

Int. J. Corros. Scale Inhib., 2026, 15, no. 3, 567-581
doi: 10.17675/2305-6894-2026-15-3-26

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