Walnut (Juglans regia L.) fruit septum alcoholic extract as corrosion inhibitor for Fe B500B steel bars in mixed acidic solution

The corrosion inhibition performance of the walnut fruit (Juglans regia L.) septum alcoholic extract for Fe B500B steel bars in a mixed acidic solution (H2SO4/HCl) is reported. Weight loss, potentiodynamic polarization, and electrochemical impedance spectroscopy measurements were performed at 298 to 318 K, with the addition of various extract concentrations. Results showed the maximum corrosion inhibition efficiency of 86.99 % for 300 mg L-1 extract added. The extract acts as a mixed-type inhibitor, predominantly affect­ing the anodic side, following Flory-Huggins adsorption isotherm. Thermodynamic analysis indicated an endothermic process with both chemisorption and physisorption on the steel bar surface. Surface characterization was conducted using ATR-FTIR, UV-vis and SEM techniques to prove the adsorption of the inhibitor molecules on the steel bar surface. Also, a possible adsorption mechanism of inhibitor molecules was proposed.