Corrosion Inhibition of Aluminum in 1 M H₂SO₄ by Tecoma Non-aqueous Extract

Tecoma extract was investigated as a green corrosion inhibitor for aluminum in 1 M H₂SO₄ solution using weight loss, potentiodynamic polarization, electrochemical impedance spectroscopy and electrochemical frequency modulation techniques. It was found that this extract presented excellent corrosion inhibition performance for aluminum and show the maximum 90.2% inhibition efficiency at 300 ppm. Polarization curves revealed that the used extract represents mixed-type inhibitor. Adsorption of used extract led to a reduction in the double-layer capacitance and an increase in the charge transfer resistance. The inhibition efficiency was improved with concentration of the extract, while decreased with improvement of corrosion temperature of the medium. The adsorption isotherm of the extract on aluminum surface conformed to the Langmuir adsorption model. Surface analysis was tested using scanning electron microscope. The results obtained from all investigated techniques are in good agreement.