Chitosan as a green inhibitor for mild steel corrosion: Thermodynamic and electrochemical evaluations

In this research, the effects of chitosan on the corrosion behavior of mild steel in 0.1 M hydrochloric acid was investigated by different approaches. According to weight loss measurements, increasing the concentration of chitosan from 0.3 to 1.8 mM, significantly reduced the corrosion rate of mild steel, for example, from 95.5 +/- 5 to 7.5 +/- 5 mpy at 298 K. The thermodynamic calculations indicate an increase in the corrosion activation energy and the enthalpy of activation when 1.8 mM chitosan was added to the aggressive solution. The electrochemical polarization technique revealed a decrease in corrosion current density which is compatible with the observed increase in the charge transfer resistance measured by electrochemical impedance spectroscopy. The EDS spectra confirmed the adsorption of chitosan on mild steel. Analyzing the surface topography of the coupons by atomic force microscopy showed a remarkable decrease in the corrosion rate of the specimens in the presence of chitosan.