Chloride threshold determination of hybrid inhibitor immersed in simulated concrete pore solution

Abstract

The hybrid inhibitor performs excellently compared to either organic or inorganic inhibitor individually. In the present studies, a fixed amount i.e. 2 wt% l-arginine (LA) and 0.25 wt% trisodium phosphate dodecahydrate (TSPDH) is considered as hybrid inhibitor and its chloride threshold is determined by open circuit potential (OCP), electrochemical impedance spectroscopy (EIS) and potentiodynamic polarization (PDP) in simulated concrete pore solution and the formed passive films are characterized by scanning electron microscopy (SEM), atomic force microscopy (AFM), X-ray photoelectron spectroscopy (XPS) and Raman spectroscopy after 240 h of immersion. The chloride threshold of this hybrid inhibitor is 6 wt% NaCl, i.e., C3 until 216 h of immersion, whereas if the amount is increased, the steel rebar leads to corrode severely. 5 wt% NaCl containing sample, i.e., C2 exhibits the noble OCP, highest impedance, and lowest passive current density attributed to the consumption of all zwitterion and phosphate ions in the formation of P-zwitterion-(Cl)-Fe, zwitterion-(Cl)-Fe and FePO4 complexes with NaCl, whereas lower or higher than this amount of NaCl, the Cl- ions either lesser or greater to be formed these complexes.