Assessments of licorice root extract as an environmentally benign corrosion inhibitor for aluminum in HCl solutions

Licorice root extract (LR) was validated as a secure and eco-friendly inhibitor of Al electrode corrosion in 1.0 M HCl solution through chemical and electrochemical methods. These outcomes proved that LR extract was a potent inhibitor. The percentage inhibitory efficacy (%IE) improved with lower temperatures and rising LR extract dosage, reaching 95.96% at 450 mg l−1 LR extract using the potentiodynamic polarization technique. Polarization curves showed that the LR extract had a mixed inhibitory effect. The inhibition was explained by the spontaneous and horizontal adsorption of the four main components of the LR extract onto the surface of the Al. Electrochemical impedance spectroscopy experiments demonstrated a single capacitive loop, implying that the corrosion reaction was controlled by a charge transfer process. The adsorption matches the Langmuir isotherm. Due to the various conditions used in each approach, the protection efficacy values obtained from the several measurements were nearly identical, with a small fluctuation. Furthermore, the thermodynamic parameters of kinetic activation and adsorption characteristics were computed and analyzed. The DFT study revealed that the active components of Licorice can undergo chemical adsorption onto the Al surface.