Performance Evaluation of a Chitosan/Silver Nanoparticles Composite on St37 Steel Corrosion in a 15% HCl Solution

A chitosan/silver nanoparticles (AgNPs/chitosan) composite has been prepared in situ using natural honey as the reducing and capping agent, and its effectiveness as an inhibitor for St37 steel in 15% HCl solution was assessed using electrochemical impedance spectroscopy (EIS), potentiodynamic polarization (PDP), dynamic electrochemical impedance spectroscopy (DEIS), and weight loss (WL) methods complemented with surface morphological examination with the aid of energy dispersive X-ray spectroscopy (EDS), atomic force microscopy (AFM), and scanning electron microscopy (SEM). AgNPs/chitosan was characterized using Fourier transformed infrared (FTIR), EDS, and SEM. The results obtained show that AgNPs/chitosan is an effective cathodic type inhibitor particularly at higher temperature and protects the metal surface by formation of a protective film. SEM, AFM, and EDS confirm the formation of an adsorbed film. The adsorption followed the Temkin adsorption isotherm; as such, the thermodynamic and kinetic parameters governing the adsorption were calculated and discussed. The values of the free energy of adsorption suggest that a mixed adsorption mechanism characterized the adsorption of AgNPs/chitosan molecules at lower temperature while chemisorption defined the adsorption process at higher temperature.