Electrochemical and gravimetric evaluation of a Zn/water hyacinth leaf extract hybrid composite as a green inhibitor for high-strength steel in acidic environment

ABSTRACT Exposure of metals to acidic environments has been a major source of corrosion, requiring immediate intervention. Consequently, there has been a huge interest in the use of hybrid composites as green corrosion inhibitors for high-strength steel. Herein, a hybrid composite inhibitor based on zinc and water hyacinth leaf extract (Zn/WHLE) was prepared and investigated for corrosion mitigation of high-strength steel pipeline in acidic media. The findings acquired from FTIR, SEM and EDX analyses confirmed the successful formation of the Zn/WHLE composite. Phytochemical screening of water hyacinth leaf extract revealed numerous inhibitive phytochemicals of phenolics, flavonoids, tannins and alkaloids. Corrosion inhibition experiments revealed an increase in the inhibition efficiency with the increasing amount of Zn/WHLE composite. Gravimetric measurements in 0.5 M HCl solution, yielded high inhibition efficiency of 90.29% using 400 ppm of Zn/WHLE after 24 h of immersion. With the same inhibitor concentration, electrochemical studies offered maximum inhibition efficiency of 86.44% and 82.91% from potentiodynamic polarization and electrochemical impedance measurements respectively. The Tafel polarization studies demonstrated that the Zn/WHLE hybrid composite acted as a mixed-type of inhibitor by affecting both cathodic and anodic sites. The Gibbs free energy of adsorption ( Δ G a d s ) obtained was -18.58 kJ/mol, indicating spontaneous and physical adsorption of the Zn/WHLE inhibitor on the steel surface. The adsorption of the Zn/WHLE inhibitor on the steel interface was found to obey the Langmuir isotherm model. Consequently, the findings of this work offers a promising environmental friendly solution to mitigate corrosion of high-strength steels during acid pickling.