Corrosion of AISI 4130 Steel Alloy under Hydrodynamic Condition in Ethylene Glycol + Water + NO2− Solution

The electrochemical behavior of steel alloy in ethylene glycol–water mixture at different solution rotating speeds was investigated by polarization curves and AC impedance measurements (EIS). The results obtained showed that corrosion rate was not changed significantly at different rotating speeds and was decreased with increasing ethylene glycol concentration. The effect of nitrite as an inhibitor was studied and high inhibition efficiency was obtained. It was found that surface passivation occurred in the presence of inhibitor. The inhibiting effect of the nitrite was explained on the basis of the competitive adsorption between the inorganic anions and the aggressive Cl− ions and the adsorption isotherm basically obeys the Flory–Huggins adsorption isotherm. Thermodynamic parameters for steel corrosion and inhibitor adsorption were determined, which revealed that the adsorption process is spontaneous.