Corrosion Inhibition of Mild Steel in Hydrochloric and Nitric Acid Solutions Using Willow Leaf Extract

Abstract

The inhibition mechanism of willow (Salix) plant leaf extract on the corrosion of mild steel in 0.5 M HCl and 0.5 M HNO₃ solutions was investigated using potentiodynamic polarization and electrochemical impedance spectroscopy (EIS) techniques, as well as Fourier transform infrared spectroscopy (FTIR) and Ultra-violet Spectrophotometry (UV). Potentiodynamic polarization curves showed that the willow leaf extract acts as a mixed type inhibitor. The impedance responses in both acidic solutions revealed that the corrosion process occurs under charge transfer control. Three adsorption isotherms including Langmuir, Kinetic-thermodynamic and Florry–Huggins were tested to clarify the mode of inhibition of willow leaf extract. The obtained data showed that willow leaf extract could serve as an effective inhibitor for the corrosion of mild steel in acidic media. However willow was more efficient in 0.5 M HNO₃ solutions than in 0.5 HCl solutions.