Design and evaluation of a MgO@MnO2@graphite hybrid nanostructure for enhanced acid corrosion protection of carbon steel

Purpose The purpose of this paper is to present the synthesis, characterization and corrosion inhibition performance of a novel MgO@MnO2@graphite hybrid nanocomposite for carbon steel protection in acidic media. The study demonstrates its high inhibition efficiency (up to 98.86% at 300 ppm) through electrochemical and surface analyses. The work also explores the underlying adsorption mechanism using thermodynamic and kinetic evaluations. These findings highlight the potential of MgO@MnO2@graphite as an effective, low-cost and environmentally friendly corrosion inhibitor, aligning with current research interests in advanced materials for industrial corrosion control. Design/methodology/approach This study used a sol–gel synthesis approach to prepare MgO and MnO2 nanoparticles, which were subsequently integrated with graphite via ultrasonication to form a MgO@MnO2@graphite nanocomposite. Comprehensive characterization was performed using X-ray diffraction, Fourier transform infrared, scanning electron microscopy-energy-dispersive X-ray, transmission electron microscopy, ultraviolet–visible, atomic force microscopy and X-ray photoelectron spectroscopy to confirm structure and morphology. The corrosion inhibition performance of the nanocomposite on carbon steel in 1 M HCl was evaluated using weight loss analysis, potentiodynamic polarization, electrochemical impedance spectroscopy (EIS) and electrochemical frequency modulation. Surface analysis further supported the protective film formation mechanism. All tests were conducted under standardized conditions and validated through repeat measurements. Findings The MgO@MnO2@graphite nanocomposite exhibited remarkable corrosion inhibition performance for carbon steel in 1 M HCl. Weight loss, electrochemical and surface analyses confirmed a concentration-dependent inhibition efficiency, reaching 98.86% at 300 ppm. Potentiodynamic polarization and EIS studies indicated mixed-type inhibition, enhanced charge transfer resistance and reduced corrosion rates. Surface analyses (AFM and XPS) verified protective layer formation. Thermodynamic and kinetic evaluations revealed a spontaneous, exothermic adsorption process involving both physisorption and chemisorption. Adsorption followed Frumkin isotherm behavior. These comprehensive findings highlight the nanocomposite’s potential as a highly efficient and stable corrosion inhibitor in aggressive acidic environments. Originality/value This study introduces a novel MgO@MnO2@graphite nanocomposite synthesized via a simple sol–gel and ultrasonication route for corrosion protection of carbon steel in acidic media. The originality lies in the synergistic integration of MgO and MnO2 with graphite, offering enhanced inhibition efficiency through a mixed physisorption-chemisorption mechanism. Comprehensive evaluation using electrochemical, surface and thermodynamic analyses demonstrated superior protection efficiency (up to 98.86%) and long-term stability. The findings provide valuable insight into designing multifunctional nanocomposites as environmentally friendly, low-cost alternatives for corrosion mitigation in industrial applications, particularly where aggressive acidic conditions are encountered.