Abstract
Corrosion inhibition is a highly effective strategy for mitigating metal degradation. However, the effect of high temperature on inhibitor effectiveness is not well documented in the literature. More specifically, the concept of critical micelle concentration (CMC), often used to select optimal inhibitor dosage, is typically based on room temperature experiments and needs to be validated over a wider range of conditions. In the research reported herein, electrochemical measurements were conducted to evaluate the performance of an alkylbenzyldimethylammonium chloride inhibitor against CO2 corrosion of mild steel at various temperatures (25°C to 80°C) in a 1 wt.% NaCl electrolyte. CMC values were also evaluated at the same temperatures using a tensiometer to investigate the connection between inhibitor concentration, micellization, and inhibition efficiency. The results showed that the performance of this quaternary ammonium-type inhibitor was extremely sensitive to temperature. The amount of inhibitor required to achieve sufficient efficiency increased considerably from 25°C to 50°C, and no sign of inhibition was observed at 80°C, even at very high inhibitor dosage. CMC values can only partially predict the minimum inhibitor concentration required to provide sufficient protection at 25°C and 50°C, but this concept failed at 80°C. It was further postulated that the structure of the adsorbed inhibitor layer significantly changed with temperature.
