CO2 saturated solutions of 3% NaCl were used to study the corrosion inhibition of mild steel samples under turbulent flow conditions at different pH values. The performance of cetyl trimethyl ammonium
bromide (CTAB) was tested with three different concentrations (20, 60 and 100 ppm) and three different pHs (3.8, 5 and 6). The rotating cylinder electrode (RCE) was used to test different turbulent flow conditions
(1000 - 5000 rpm). It was found that the inhibitor performance is function of its concentration and pH. A localised corrosion process was found on the surthce examination and a further research was carried out to
determine its causes. It was demonstrated with the use of cyclic anodic polarisation curves and surface examinations that the localised corrosion process does not occur at a specific rotation speed. With the use
of potentiostatic experiments, the effect of shear stress and the instantaneous changes in Ecorr observed when the rotation speed was increased were simulated. The electrochemical measurements and the surface examinations, showed that the changes in Ecorr to more positive values are more important in producing the localised process, and removing the electrostatically adsorbed inhibitor from the surface sample, than increases in shear stress.
Key words: CO2 corrosion, turbulent flow, localised corrosion, inhibitors, electrochemistry.