Pumpkin seeds as an eco-friendly corrosion inhibitor for 7075-T6 alloy in 3.5% NaCl solution: Electrochemical, surface and computational studies

For the aeronautics industry, constraints of mechanical strength are paramount. Aluminum and its alloys are widely used for various household and industrial applications. Among the various established and identified aluminum alloys, 7075 alloy, which is an aluminum-zinc, acquires the best mechanical strength. However, this is sensitive to certain localized corrosion phenomena such as pitting corrosion. Pumpkin seeds (PS) were evaluated as a corrosion inhibitor for aluminum alloy 7075-T6 in 3.5% NaCl solution using electrochemical, surface and theoretical studies. PS showed highest inhibition efficiency of 95% at its 1 g/L concentration (298 K). Furthermore, the Pumpkin seeds (PS) acted as a cathodic inhibitor. Adsorption of Pumpkin seeds (PS) on Aluminum alloy surface corresponds to the Langmuir adsorption isotherm. Surface studies carried out using scanning electron microscope (SEM), atomic force microscope (AFM) and X-ray Diffraction (XRD) provide good supports to the polarization and EIS studies. Surface studies also validate that PS becomes effective by adsorbing on the metallic surface. Using DFT investigation, it was derived that effectiveness of the major phytochemical followed the sequence: 9,12-Octadecadienoic acid (Z, Z)-> linoleic acid > palmitic acid.