Investigating the synthesized sodium gluconate-loaded chitosan microspheres on mild steel corrosion inhibition in acidic medium

In this research, the sodium gluconate-loaded chitosan microspheres (SG/CM) are prepared by negative pressure impregnation after chitosan (CS) hydrothermally synthesized with vanillin (VA) to form chitosan microspheres (CM), which is in shape of ellipsoidal spheroid. The structures of the prepared micron materials are investigated by Fourier transform infrared spectroscopy (FTIR), while tungsten filament scanning electron microscopy (SEM) and transmission electron microscopy (TEM) are used to characterize the morphology of the prepared. Moreover, the thermogravimetric characterization reveals that loading sodium gluconate made it more thermally stable. The corrosion inhibition performance of CS, CM, and SG/CM is investigated in 0.1 mol/L HCl by electrochemical impedance spectroscopy (EIS), indicating an increase efficiency for inhibitors at higher concentrations, and the optimum is achieved by SG/CM at 200 mg/L, corresponding to weight loss measurements. The potentiodynamic polarization (PDP) test shows the best inhibition efficiency, 92.01% for SG/CM, which is superior to 52.23% for CS and 75.91% for CM. The surface features of corroded samples are investigated by Leica optical microscopy. Additionally, the inhibition mechanism of SG/CM is studied by building the Langmuir adsorption model, revealing that the inhibitory molecule occupies only one site on the themetallic surface.