ISSN print edition: 0366-6352 ISSN electronic edition: 1336-9075 Registr. No.: MK SR 9/7 Published monthly

Synergistic corrosion inhibition of mild steel in 0.5 M H₂SO₄ by sodium benzoate, onion extract, and chitosan: mechanistic and electrochemical insights

Ameena Kousar, P. T. Sowmya, Anitha Sudhir, S. K. Giridarshan, and V. Bhavana

Department of Chemistry, Vidyavardhaka College of Engineering, Visvesvaraya Technological University, Mysuru, India

E-mail: ptsowmya8@gmail.com

Received: 12 January 2026  Accepted: 30 April 2026

Abstract:

Corrosion of mild steel in acidic environments remains a serious industrial challenge, particularly during acid cleaning and pickling operations. The aim of this work was to develop and evaluate a ternary green hybrid inhibitor combining sodium benzoate, onion extract, and chitosan for corrosion protection of mild steel in 0.5 M H₂SO₄, which has not been previously reported as a single integrated system. The corrosion inhibition performance of individual, binary, and ternary formulations was assessed using open circuit potential monitoring, potentiodynamic polarization, and electrochemical impedance spectroscopy. The ternary benzoate–onion extract–chitosan system exhibited the most stable electrochemical behavior, with a marked reduction in corrosion current density and a significant increase in charge-transfer resistance compared to the other formulations. The enhanced inhibition performance arises from the complementary action of organic adsorption and polymer-assisted film formation, leading to a compact protective layer on the steel surface. This study provides a new, sustainable ternary hybrid strategy that advances previous single- and binary-component green inhibitors for corrosion protection in acidic media.

Keywords: Mild steel corrosion; Green corrosion inhibitor; Electrochemical impedance spectroscopy (EIS); Tafel polarization

Full paper is available at www.springerlink.com.

DOI: 10.1007/s11696-026-04991-3

Chemical Papers 80 (9) 10043–10062 (2026)