Corrosion Inhibitive Action and Adsorption Behaviour of Justicia Secunda Leaves Extract as an Eco‐Friendly Inhibitor for Aluminium in Acidic Media

Abstract

The extract of Justicia secunda (JS) leaves was investigated as an eco‐friendly corrosion inhibitor of aluminum in 0.5 M HCl using weight loss, electrochemical impedance spectroscopy (EIS), potentiodynamic polarization (PDP), and scanning electron microscopy (SEM) techniques. The inhibitor concentrations used ranged from 50 to 250 ppm at 30, 40, and 50oC. Results show that Justicia secunda acts as a good inhibitor for aluminum. Its efficiency increased with increasing inhibitor concentration but decreased with increasing temperature. Maximum inhibition efficiency as high as 94.3% was found at 30°C for 250 ppm of the inhibitor with the weight loss technique. Tafel polarization results show that the extract acts as a mixed-type inhibitor. The Nyquist plots indicated decreasing double-layer capacitance and increasing charge transfer resistance on increasing JS concentration. The inhibition action occurred through the physical adsorption of the extract on the aluminum surface. The adsorption process was found to follow Langmuir adsorption isotherm. The formation of a protective film on the metal surface was confirmed by scanning electron microscopy.