Cationic Surfactant - Zn+2 Systems as Mixed Corrosion Inhibitors for Carbon Steel in a Sodium Chloride Corrosive Medium

Benzyl dimethyl dodecyl ammonium chloride-zinc ion system, as quaternary ammonium salt (QA-Zn +2 ), was investigated as corrosion inhibitor for carbon steel in a 2.0 M sodium chloride solution, by different techniques such as weight loss, open circuit potential, potentiodynamic polarization and electrochemical impedance spectroscopic techniques.The inhibition efficiency of the used system (QA-Zn +2 ) increases with increasing mixed inhibitor concentrations and with rising temperatures.A synergistic effect exists between QA and Zn +2 .Potentiodynamic polarization curves indicate that the used system mainly acts as an anodic mixed inhibitor.The polarization resistance values were (Rp) increased, and the interface capacitance (Cdl) was decreased in the mixed inhibitor system (QA-Zn +2 ) presence, more than in the case of individual inhibitors.The corrosion inhibition is due to the adsorption of (QA-Zn +2 ) onto the metal surface, and the formation of a barrier film that separates the metal from the corrosive medium.The maximum inhibition efficiency of 98% was obtained at 200 QA and 50 ppm Zn +2 of the mixed inhibitor system, due to a synergistic effect.