Eco-friendly inhibitors for sustainable corrosion protection of mild steel under oilfield acidizing conditions

This study investigates the effect of temperature (30-60 °C) on the corrosion behavior of mild steel in 15% hydrochloric acid, in the absence and presence of four novel, eco-friendly corrosion inhibitors derived from ethanolic extracts of agro-industrial and botanical wastes. Electrochemical impedance spectroscopy (EIS), potentiodynamic polarization, adsorption isotherm, and activation parameter determination were employed, alongside surface morphology analysis using scanning electron microscopy (SEM). All extracts acted as mixed-type inhibitors, achieving high efficiency at low concentrations (0.010-0.600 g/L), with inhibition rates decreasing slightly from 85.8 to 78.4% at 30 °C to 81.9-61.8% at 60 °C. SEM confirmed the formation of a protective surface film, while adsorption followed Langmuir, Flory-Huggins, and Temkin isotherms. Thermodynamic analysis indicated a spontaneous process involving both physisorption and chemisorption. These findings highlight the thermal stability, strong adsorption capability, and practical potential of the studied plant-based extracts as sustainable, non-toxic alternatives to conventional inhibitors for use in harsh oilfield acidizing and descaling operations.