Corrosion Inhibition of Carbon Steel in Carbonate Acidizing at Elevated Temperature

Abstract This paper presents an investigation on the performance of corrosion inhibitors in reducing corrosion loss of N80 steel coupons at high temperature in 15 wt.% and 28 wt.% HCl solutions. This work studied the effect of temperature and acid concentration on corrosion inhibitor performance and provided an efficient corrosion inhibitor for application at elevated temperature of 120°C. Five corrosion inhibitors including Mannich base derivatives and pyridine quaternary ammonium salt were selected. The corrosion rates of N80 steel in concentrated HCl solution with and without corrosion inhibitor were evaluated by gravimetric method and the surface of steels after corrosion tests were characterized by microscopy. The results showed that the corrosion rate of N80 steel in 15 wt.% HCl at 120°C was much higher than that at 90°C. As a result, higher concentration of corrosion inhibitor was needed to reduce the corrosion to an acceptable value of 0.05 lb/ft2. The corrosion rate could be reduced to 0.0035 lb/ft2 in 15 wt.% HCl at 120°C. Increasing the HCl concentration to 28 wt.% at 120°C, the corrosion inhibitor concentration required was several times as much as the dosage for 15 wt.% HCl.