Theoretical and surface/electrochemical investigations of walnut fruit green husk extract as effective inhibitor for mild-steel corrosion in 1M HCl electrolyte

The present paper has studied the corrosion inhibition property of Juglone extracted from walnut (Juglans regia L.) green husk for mild steel samples exposed to an acid electrolyte (1 M HCl). Besides, via computer modelings, the attraction forces of the inhibitors/metal surface were explored. The corrosion inhibition efficiency of the organic inhibitor was evaluated using potentiodynamic polarization as well as EIS techniques. In addition, XPS, FT-IR, SEM, AFM, and UV–visible spectroscopy have been used to study the inhibition mechanism of the agricultural waste extract in the corrosive media. Quantum chemical calculations based on DFT theory and molecular dynamic simulations were investigated on the adsorbed Juglone inhibitors. The obtained results indicated that the efficiency of the used inhibitor was enhanced with increasing the concentration of green corrosion inhibitor (GCI) and reached 95% in the presence of 800 ppm after 8 h immersion. Moreover, the average roughness of the exposed metal to the corrosive electrolyte decreased from 68.2 ± 8.3 nm for the blank solution to 3.4 ± 0.3 nm for the solution containing 800 ppm GCI. Furthermore, the Tafel extrapolated polarization results revealed that the extracted GCI functioned as a mixed-type corrosion inhibitor. Finally, the obtained analysis results are supported by theoretical data.