Kinetic and mechanistic study of CO2 corrosion inhibition by cetyl trimethyl ammonium bromide

The kinetics of the inhibition of carbon dioxide (CO2) corrosion on high purity iron (Fe) electrodes by cetyl trimethyl ammonium bromide (CTAB) were investigated in order to elucidate the mechanism of inhibition. The test condition was: 25 °C, 3 wt.% NaCl brine, pH 4, 1 bar CO2 partial pressure. The inhibition process was studied by electrochemical methods and by X-ray photoelectron spectroscopy (XPS). The inhibition was found to be a combination of two processes: first a rapid process (order of minutes) connected to diffusion limited adsorption of the inhibitor, leading to the inhibition of the anodic part reaction, and a second slower process (order of hours) leading to a reduction in the corrosion rate through the inhibition of the cathodic part reaction(s).