Cross-linked aminated lignophenol derived from lignin: synthesis, characterization and corrosion inhibition performance for carbon steel in 1 M HCl

• S.G. Yuldashova^1,2, N.Sh. Muzaffarova², A.K. Nomozov^1,3,4, M.J. Abduvalieva¹, K.A. Karimov⁵, Kh.N. Eshankulov⁶, F. Ismoilov⁷, U.M. Shomuradov⁸, K.Kh. Abduvalieva⁹ and S.E. Karaev¹⁰

¹ Chemical Engineering, Termez State University of Engineering and Agrotechnologies, Termez, 190100, Uzbekistan
² Department of Medical and Biological Chemistry, Termez branch of Tashkent State Medical University, Termez, 190111, Uzbekistan
³ Department of Natural Sciences, Termez University of Economics and Service, Farovon Street 4-b, Surkhandarya, Termez, 190111, Uzbekistan
⁴ Department of Microbiology and Epidemiology, Termez Branch of Tashkent Medical University, Termez, 190111, Uzbekistan
⁵ Theoretical Mechanics Department, Tashkent State Technical University, Tashkent, 100179, Uzbekistan
⁶ Department of Physical Chemistry, Termez State University, Termez, 190111, Uzbekistan
⁷ Department of Chemical Engineering and Biotechnology, Karshi State Technical University, Karshi, Uzbekistan
⁸ Karshi State Technical University, Karshi, Uzbekistan
⁹ Jizzakh State Pedagogical University. Jizzakh, 130100, Uzbekistan
¹⁰ Department of General Chemistry and Chemical Technologies, Denov Institute of Entrepreneurship and Pedagogy, Denov, Uzbekistan

Abstract: A lignin-derived material designated LPPD was prepared through sequential phenolation, Mannich-type amination with p-phenylenediamine, and treatment with formaldehyde to promote cross-linking. FTIR spectroscopy showed features consistent with hydroxyl, aromatic, aliphatic, and nitrogen-containing functionalities, although the precise molecular structure and extent of cross-linking were not established. The corrosion inhibition performance of LPPD toward St2 carbon steel in 1.0 M HCl was investigated using gravimetric measurements, potentiodynamic polarization (PDP), electrochemical impedance spectroscopy (EIS), scanning electron microscopy (SEM), and atomic force microscopy (AFM). Gravimetric results indicated increasing inhibition efficiency with inhibitor concentration, reaching approximately 95% at 100 mg·L^–1 and 333 K. PDP measurements showed a decrease in corrosion current density from 12.98 to 0.56 mA·cm^–2, corresponding to approximately 96% inhibition efficiency. The polarization behavior was consistent with mixed-type inhibition with a predominant cathodic contribution. EIS showed increased impedance with LPPD addition, with the fitted charge-transfer resistance increasing from 267.91 to 14951 Ω·cm². SEM observations indicated less surface deterioration in the presence of LPPD, while AFM revealed differences in surface topography. These morphological observations do not establish the chemical identity of a surface layer. Overall, the results support the corrosion inhibition performance of LPPD for St2 carbon steel under the investigated conditions. The detailed adsorption mechanism, long-term stability, and applicability to other corrosive environments remain to be established.

Keywords: lignin-derived inhibitor, aminated lignophenol, carbon steel, hydrochloric acid, electrochemical impedance spectroscopy, potentiodynamic polarization

Int. J. Corros. Scale Inhib., 2026, 15, no. 4, 338-360
doi: 10.17675/2305-6894-2026-15-4-14

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