Ocimum Basilicum Seeds as a New Natural Corrosion Inhibitor for AA7075-T6 Aluminum Alloy in Nacl Solution: Electrochemical, Thermodynamic, Surface, and Theoretical Studies

The use of aluminum and its alloys is widespread in the industry, especially in the aeronautic sector. AA7075-T6 (aluminum–zinc) has the best mechanical properties of all aluminum alloys. However, its corrosion resistance is low. In this work, ocimum basilicum seeds (OBS) have been evaluated as a corrosion inhibitor for the AA7075-T6 in 3.5% NaCl solution, using electrochemical methods, surface analysis, and theoretical investigation. The obtained results show that OBS significantly decreases the reactivity of the alloy, and thus provides more effective corrosion protection. The inhibition efficiency increases as the inhibitor concentration increases, reaching a maximum of 93% for 0.50 g/L. Furthermore, the IE measurement shows that OBS behaved as a mixed-type inhibitor. Electrochemical impedance spectroscopy (EIS) measurements corroborate these results and show that OBS increases the corrosion resistance of the aluminum alloy 7075 T-6 in 3.5% NaCl solution. SEM-EDAX and AFM images showed the presence of OBS on the surface of aluminum due to its adsorption. To further investigate the reactivity of the level 6-31G (d, p) was examined using DFT (B3LYP) approach. The molecular dynamics simulations have shown that the OBS is adsorbed in parallel mode on the surface of aluminum. In addition, the adsorption energy (E_ads) shows the stability of the adsorptive system and confirms the reliability of our experimental results.