Βackground: Corrosion of carbon steel is one of the major challenges in process industries, and the use of organic inhibitors is considered an effective approach for its control. Diminazene, as a polycationic compound, has the potential to form a protective layer on the metal surface.
Aim: This study aims to evaluate the efficiency of diminazene as a corrosion inhibitor for carbon steel and to investigate the influence of environmental and kinetic factors, including solution type, temperature, pH, solution aging time, and electrode immersion duration.
Methodology: Electrochemical tests, including electrochemical impedance spectroscopy (EIS) and Tafel polarization, were performed in 0.5 M HCl, 0.5 M H₂SO₄, 0.5 M NaOH, and 3.5 wt.% NaCl solutions. The effects of temperature, pH, and kinetic parameters, including solution aging time and the duration of electrode exposure to the solution, were investigated. AFM surface analysis was also employed to evaluate the morphological changes on the steel surface.
Findings: Diminazene is a mixed type inhibitor whose performance is concentration dependent and shows its highest efficiency in acidic media. Its inhibition efficiency was approximately 90% in sulfuric acid, 80% in hydrochloric acid, about 35% in the saline environment, and only around 8% in alkaline NaOH. Increasing temperature (up to 45 °C), solution aging time, and the duration of metal–solution contact (up to 48 h) led to a gradual decrease in inhibition performance. pH variation also produced distinct behaviors: in HCl, increasing pH enhanced the stability of the adsorbed layer, whereas in H₂SO₄ high efficiency was achieved only at very low pH values. AFM results further confirmed the formation of a more stable film in the sulfuric acid environment and a reduction in localized attack in hydrochloric acid.
Conclusions: Diminazene is an effective corrosion inhibitor for carbon steel; however, its performance depends strongly on the nature of the environment and the o