Investigations of Terminalia chebula Ritz. extract (TCE), Garcinia indica Choisy extract (GIE), and Coriandrum sativum L. extract (CSE) as corrosion inhibitors for 6063 Al alloy in phosphoric acid (H3PO4) of 0.5 M, 1.0 M, and 2.0 M using potentiodynamic polarization and electrochemical impedance spectroscopy techniques were carried out. The optimal inhibitor concentrations were varied in the temperature range of 30–50 °C at 5 °C interval. Scanning electron microscope/energy-dispersive X-ray spectroscopy (SEM/EDX) technique was used to characterize the coupon surfaces before and after corrosion tests. Inhibition efficiency results with the optimal concentrations of inhibitors were 95.52% for the addition in 0.4 g L−1 of GIE at 50 °C, 91.64% for the addition in 0.4 g L−1 of TCE at 30 °C, and 90.06% for the addition in 0.5 g L−1 of CSE at 30 °C. The activation and adsorption parameters in the presence of inhibitor suggested the adsorption mechanisms were of chemisorption of GIE and physisorptions of TCE and CSE. Langmuir adsorption isotherm was followed. A suitable inhibition mechanism was proposed. The SEM revealed cracks and roughness in the sample without inhibitor, while the surface at an optimal concentration of 0.4 g L−1 of inhibitor had a smooth surface which was accomplished by EDX studies.
All Science Journal Classification (ASJC) codes
- Materials Science (miscellaneous)
- Mechanics of Materials
- Mechanical Engineering
- Materials Chemistry