Role of L-arginine on the formation and breakdown of passive film onto the steel rebars surface in chloride contaminated concrete pore solution

In the present study, different amounts of L-arginine (LA) i.e. Zwitterion have been used as an eco-friendly corrosion inhibitor to study its effect on the mitigation of the steel rebars corrosion in 0.17 M NaCl added simulated concrete pore (SP) solution. Potentiodynamic polarization, open circuit potential (OCP), and electrochemical impedance spectroscopy (EIS) have been used to understand the corrosion kinetics and mechanism for the formation of passive film at steel rebar/solution interface with exposure periods. The characterization of passive films after 144 h of exposures were performed by scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS), and Raman spectroscopy. Cl⁻ ions help in the formation of Zwitterion-(Cl)-Fe complex in the presence of LA containing solution which led to stabilize the passive film resulting improvement in polarization resistance (R_p). The steel rebar exposed to 0.115 M LA containing SP + 0.17 M NaCl solution exhibited around 96% inhibition efficiency after 144 h of exposure. Raman spectroscopy of passive film reveals adsorption of LA and formation of goethite and maghemite. A schematic has been proposed to derive the adsorption mechanism of LA in the presence of Cl⁻ ions and form Zwitterion-(Cl)-Fe complex, therefore, enhanced corrosion resistance was observed.