Corrosion inhibition of mild steel using eco-friendly porous nanocarbon derived from waste mango kernels: a step towards sustainability

Abstract

The pervasive corrosion of mild steel in acidic media poses a significant challenge in various industrial applications. While existing synthetic corrosion inhibitors are effective, their high cost and environmental toxicity necessitate the development of more sustainable alternatives. In this study, we present a novel approach to corrosion mitigation employing a porous nanocarbon synthesized from mango kernels, a sustainable source of agricultural waste. The CNS inhibitor was synthesized via pyrolysis at 800 °C, yielding a high surface area (1090.2 m² g⁻¹) as confirmed by BET analysis. FE-SEM revealed a well-developed spherical morphology with an average particle size of 60–70 nm. The corrosion inhibition efficiency of CNS was evaluated for mild steel in 1 M HCl using a combination of electrochemical techniques, including open circuit potential, potentiodynamic polarization (PDP), and electrochemical impedance spectroscopy. The CNS derived from waste mango kernels, exhibited excellent inhibition performance, achieving an efficiency of up to 87.1% at 800 ppm. PDP results revealed a mixed-type inhibition mechanism with suppression in both anodic and cathodic reactions. The thermodynamic parameter, adsorption free energy () of about −20.0 kJ mol⁻¹, indicates a spontaneous process and predominantly physical adsorption. Adsorption behavior was consistent with the Langmuir isotherm model. Surface analyses using SEM, EDS, optical profilometry, and water contact angle measurements corroborated the formation of a protective inhibitor film on the steel surface. These findings highlight the potential of bio-waste-derived materials as a sustainable and environmentally benign corrosion inhibitor for mild steel in acidic environments.