Effect of Volatile Corrosion Inhibitor Dosage Towards Top and Bottom of the Line Corrosion

Abstract

AbstractThe objectives of this work are to determine the emulsion tendency of VCI at varying concentrations, and the effect of VCI dosage on corrosion of X65 carbon steel exposed to top as well as bottom-of-line conditions. A series of corrosion experiments was conducted to simulate as closely as possible to a sweet CO2 pipeline environment. The main parameter was the VCI dosage where it was varied from 0 ppm (blank) to 1500 ppm. The corrosion experiment was conducted in a 2.0 L top-of-line corrosion testing unit at 1 bar CO2, 60 ℃ open system. Corrosion rate measurements were performed at the top and bottom-of-line for an exposure time of 7 days. Prior to the corrosion experiment, a pre-qualification test of VCI was conducted to determine the emulsion tendency of VCI at concentration variants mentioned earlier. The emulsion tendency test showed that the intensity of the emulsion increased with concentration where at 250 ppm VCI had the least tendency to emulsify. As for the top-of-line corrosion rate, the result revealed an 83% reduction in uniform corrosion rate when the concentration was increased from 0 to 250 ppm. On the other hand, when compared with 0 ppm VCI (blank), a 99% reduction of uniform corrosion rate can be observed in all concentrations from 250 to 1500 ppm VCI but extensive localized corrosion at 250 ppm and 750 ppm VCI was observed at bottom-of-line.KeywordsSweet corrosionInternal corrosionConcentration