The synergistic inhibition effect of oleic-based imidazoline and sodium benzoate on mild steel corrosion in a CO2-saturated brine solution

The corrosion inhibition of oleic-based imidazoline (OIM) and sodium benzoate (SB) on mild steel in a CO2-saturated solution was studied using a weight-loss method and a potentiodynamic polarization technique. The dependence of the impendence response on the immersion time (within 1 h) in the inhibited solution was measured using electrochemical impedance spectroscopy (EIS). The results show that OIM can protect mild steel from CO2 corrosion to some extent, and its inhibition can be strengthened by using it in combination with SB. The synergistic inhibition effect of OIM and SB is obvious. The EIS measurements reveal that when the immersion time is longer than 20 min, the charge transfer resistance value of the steel inhibited by OIM with SB is significantly higher than that of steel inhibited by OIM alone. The zero charge potentials of the steel in solution with and without OIM were also measured using EIS. Based on these results and an X-ray photoelectron spectroscopy analysis, an adsorption model was proposed to elucidate the synergistic mechanism between OIM and SB.