Abstract
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 (R-p) 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.