Kinetic and thermodynamic studies of AISI 4130 steel alloy corrosion in ethylene glycol-water mixture in presence of inhibitors

The electrochemical behavior of steel alloy in ethylene glycol-water mixture was investigated by electrochemical methods. The results obtained showed that corrosion rate was decreased with increasing ethylene glycol concentration. The effect of inorganic inhibitors including NO3−, NO2−, Cr2O72− and CrO42− were studied using electrochemical techniques where the highest inhibition efficiency was obtained for CrO42−. In the presence of chromate the inhibitor efficiency increased with its concentration. The inhibiting effect of the chromate 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 Langmuir adsorption isotherm. Thermodynamic parameters for steel corrosion and inhibitor adsorption were determined and reveal that the adsorption process is spontaneous. Also, a phenomenon of both physical and chemical adsorption is proposed.